Process for the simultaneous production of xylitol and ethanol

ABSTRACT

Effective processes are provided for the production of xylitol and ethanol and other products from solutions derived from lignocellulose-containing material in biomass. The solutions can be hydrolyzed or partially hydrolyzed before being fermented with microbes. The fermented solution can be distilled and can be subsequently separated, such as, by chromatographic separation, membrane separation, etc. The recovered xylitol solution can be crystallized to provide pure xylitol crystals.

RELATED APPLICATIONS

[0001] This Application is a continuation-in-part (CIP) of U.S. Ser. No.08/928,893 filed Sep. 12, 1997, which is a continuation of U.S. Ser. No.07/910,133 filed Jul. 14, 1992, now abandoned.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a process for the production ofxylitol and/or ethanol from lignocellulose-containing material.

[0003] Xylitol is a naturally occurring sugar alcohol which is formed inthe reduction reaction of xylose and which corresponds to “normal” sugarin sweetness and low in caloric content (i.e. 2.4 kcal/g). Xylitol isfound in small quantities in many fruits and vegetables and is alsoproduced in the human body as a normal metabolic product. Xylitol is avery good special sweetener in different connections on account of itscertain metabolic, dental and technical properties. Desirably, thexylitol metabolism is independent of the insulin metabolism, andtherefore also diabetics can use xylitol. Xylitol also has a retardingeffect on the bowel and may have utility in reducing diets. Furthermore,it has been found that xylitol does not cause caries but has aanti-cariogenic effect.

[0004] Despite the many advantages of xylitol, its use has been ratherrestricted. The reason for this is the relatively high price of xylitol,which in turn is a result of the difficulties of producing xylitol on alarger scale.

[0005] Xylitol has earlier been produced from xylan-containing materialsby hydrolysis, in which process a monosaccharide mixture containing e.g.xylose is obtained. Xylose is then converted to xylitol, generally inthe presence of a nickel catalyst, such as Raney nickel. A number ofprocesses for the production of xylose and/or xylitol from axylan-containing material have been described in the literature in thisfield. As examples may be mentioned U.S. Pat. No. 3,764,408 (Jaffe atal.), U.S. Pat. No. 4,066,711 (Melaja at al.), U.S. Pat. No. 4,075,406(Melaja at al.), U.S. Pat. No. 4,008,285 (Melaja at al.) and U.S. Pat.No. 3,586,537 (Steiner at al.).

[0006] These prior processes are all multi-step processes which arerelatively costly and often have inadequate efficiency. The greatestproblems reside in the effective, high yield separation of xylose and/orxylitol from polyols and other hydrolysis and conversion products andthe use of the by-products which are produced in large quantities in theprocess. Purification of the preceding can be very exacting becausecatalysts used in the reduction reaction of xylose are very sensitive.The purity of the final product often depends on the extent that thexylitol can be separated from the other products produced in thereduction reaction.

[0007] It is known that several yeast strains produce reductase enzymeswhich catalyze the reduction of sugars into corresponding sugaralcohols. Certain Candida strains have been reported to produce xylitolfrom xylose (Ditzelmullez, G. at al.: FEMS Microbiology Letters 25(1985), pp. 195-198, Kitpreechavanich, M. at al.: Biotechnology LettersVol. 6 (1984), pp. 651-656, Gong, C-S. at al.: Bioztechnology LettersVol. 3 (1981), pp. 130-135). However, these studies have been carriedout on a laboratory scale only, and the literature in this field has notdisclosed processes wherein pure xylitol is separated from thefermentation product.

[0008] The Applicants' copending U.S. patent application Ser. No.297,791 filed on Jan. 17, 1989, now U.S. Pat. No. 5,081,026, andpublished as WO-A-9008193, describes a process for the production ofpure xylitol from plant material using chromatographic separationfollowing hydrolysis and fermentation. However, in this process themajority of the raw material can be lost as a worthless waste material.If a greater part of the raw materials could be converted to commercialproducts, this would essentially improve the economy of the overallprocess.

[0009] Ethanol is a well-known compound which has a wide use. Ethanolhas attracted interest as an alternative liquid fuel. If the ethanolproduction process only uses energy from renewable energy sources, nonet carbon dioxide is added to the atmosphere, making ethanol anenvironmentally beneficial energy source.

[0010] It is known that ethanol can be produced from cellulose andhemicellulose by fermenting with a suitable yeast strain. The productionof ethanol from D-xylose has been described in U.S. Pat. No. 4,368,268(C-S. Gong), which is directed to the manufacturing of mutants thatproduce ethanol in high yields, and in Biotechnology and BioengineeringSymp. 12 (1982), pp. 91102, McCracken, L. & Gong, C-S., which isdirected to fermentation with thermotolerant yeasts.

[0011] Ethanol production from lignocellulosic material can comprise thefollowing steps: (1) degradation of the lignocellulosic structure to afermentable substrate, (2) fermentation of the fermentable substrate,and (3) distillation of the fermentation broth to obtain ethanol.

[0012] In the past, there have been problems encountered in theefficient conversion of the lignocellulosic hydrolysates to ethanol.First, after pretreatment, the hydrolysate contains not only fermentablesugars, but also a broad range of compounds which often have inhibitoryeffects in the microorganisms used for fermentation. The composition ofthese compounds depends upon the type of lignocellulosic material usedand the chemistry and nature of the pretreatment process. Second, thehemicellulose hydrolysates contain not only hexoses but also pentoses.The pentose fraction in hemicellulose comprises mainly xylose, butdepending on the raw material origin, the arabinose fraction may besubstantial. While some hexoses can readily be fermented, pentoses aremore difficult to ferment.

[0013] Lignocellulosic materials are composed of mainly cellulose,hemicellulose, and lignin. Cellulose is a linear, crystalline polymer ofβ-D-glucose units. The structure is rigid and harsh treatment is usuallyrequired to break down cellulose. Hemicellulose has usually as a maincomponent linear and branched heteropolymers of L-arabinose,D-galactose, D-glucose, D-mannose, D-xylose and L-rhamnose. Thecomposition of hemicelluose varies with the origin of thelignocellulosic material. The structure is not at least totallycrystalline and is therefore usually easier to hydrolyze than cellulose.Examples of lignocellulosic materials considered for ethanol productionare hardwood, softwood, forestry residues, agricultural residues, andmunicipal solid waste (MSW). Both cellulose and hemicellulose can beused for ethanol production. The pentose content in the raw material isof importance as pentoses are often difficult to ferment to ethanol. Thepentose content can comprise 6-28% of the total dry matter. To achievemaximum ethanol yield, all monosaccharides should be fermented. Softwoodhemicellulose contains a high proportion of mannose and more galactoseand glucose than hardwood hemicellulose whereas hardwood hemicelluloseusually contains a higher proportion of pentoses like D-xylose andL-arabinose.

[0014] The degradation of the lignocellulosic structure often requiresmany steps. The first step can comprise prehydrolysis in which thehemicellulose structure is broken down. The second step can comprise thehydrolysis of the cellulose fraction in which lignin will remain as asolid by-product. The two hydrolyzed streams can be fermented to ethanoleither together or separately, whereafter they can be mixed together anddistilled.

[0015] As previously discussed, during the degradation of thelignocellulosic structure, not only fermentable sugars are released, buta broad range of compounds, some of which can inhibit the effectivenessof the microorganism used for fermenting. The amount and nature ofinhibiting compounds depends on the raw material, the prehydrolysis andhydrolysis procedures, and the extent of recirculation in the process.Fermentation inhibitors in lignocellulosic hydrolysates can be dividedinto several groups depending on their origin. Substances releasedduring prehydrolysis and hydrolysis include acetic acid, which isreleased when the hemicellulose structure is degraded and extractives.The extractives can comprise terpenes, alcohols, and aromatic compoundssuch as tannins. The inhibitory effect of acetic acid is pH dependent.The fermentability of a lignocellulosic hydrolysate can be improved byraising the pH. Furthermore, a group of inhibitors, such as furfural,5-hydroxymethyl furfural, laevulinic acid, formic acid, and humicsubstances are often produced as by-products in prehydrolysis andhydrolysis due to the degradation of sugars. Moreover, lignindegradation products are often produced in prehydrolysis and hydrolysis.This group of inhibitors includes a wide range of aromatic andpolyaromatic compounds with a variety of substituents. Also, products ofthe fermentation process, such as ethanol, acetic acid, glycerol, andlactic acid, inhibit the microorganism. The influence of these compoundswill be especially evident in recirculation systems. Furthermore, metalsreleased from the equipment and additive such as sulfur dioxide (SO₂)can also inhibit fermentation.

[0016] It is, therefore, desirable to provide an improved method toproduce ethanol, as well as perhaps other important products, such asxylitol, from lignocellulose-containing material in biomass.

BRIEF SUMMARY OF THE INVENTION

[0017] An improved method is provided to produce ethanol, as well asperhaps other important products, such as xylitol, fromlignocellulose-containing material in biomass. Advantageously, themethod is effective, economical and attractive.

[0018] In the method, lignocellulose-containing material fromxylan-containing matter in biomass comprising pentose and hexose, isprocessed by hydrolysis or partial hydrolysis to produce a processedsolution comprising free pentoses and hexoses. The processed solutioncan be fermented with microbes to produce a fermented solutioncomprising fermented ethanol and spent microbes. During fermenting, asubstantial amount of hexose in the processed solution is converted toethanol. Fermented liquid derived from the fermented solution can bedistilled to produce distilled ethanol. Advantageously, the distilledethanol comprises a greater concentration of ethanol by weight on aliquid basis than the ethanol in the fermented solution.

[0019] The lignocellulose-containing material can comprise at least onelignocellulosic material, such as cellulose, hemicellulose, or lignin.The xylan-containing matter can comprise one or more of the following:wood, softwood as pine and spruce hardwood as alder, aspen, birch,beech, eucalyptus, maple, poplar, willow, plants as plant constituents,grain as wheat, barley, rice, rye and oat, particulates of grain asstraw, hulls, husks, fiber, shells, stems, , corn cobs, corn straw, cornfiber, nutshells, almond shells, coconut shells, bagasse, cotton seedbran, cotton seed skins, wood chips, sawdust, woodpulp, processed paper,spent sulphite liquor, spent liquor from paper processing, spent liquorfrom woodpulp processing, sulphite cooking liquor, or liquids derivedfrom any of the preceding.

[0020] The processed solution can comprise biomass hydrolysates. Thebiomass hydrolysates can be obtained by: direct acid hydrolysis of thebiomass, enzymatic prehydrolysate obtained by prehydrolysis of thebiomass with steam or acetic acid, acid hydrolysis of prehydrolysateobtained by prehydrolysis of the biomass with steam or acetic acid, or asulphite pulping process. The biomass hydrolysates can also comprise orbe derived from: spent sulphite pulping liquor, acid spent sulphiteliquor, spent liquor from softwood pulping before hexoses are removed,spent liquor from softwood pulping after hexoses are removed, spentliquor from hardwood pulping, spent liquor from digestion of thebiomass, spent liquor from hydrolysis of the biomass, spent liquor fromsolvent-based pulping, spent liquor from ethanol-based pulping, spentliquor from sulphate-prehydrolysis pulping, mother liquor fromcrystallization of xylose, and diluted runoff of xylose crystallizationof sulphite spent pulping liquor derived solution.

[0021] The pentose can comprise at least one pentose-containingmaterial, such as D-xylose or L-arabinose. During fermentation,L-arabinose in the processed solution can be reduced (converted) toarabinitol. The hexose can comprise at least one hexose-containingmaterial, such as: D-glucose, D-galactose, L-rhamnose, D-mannose, orother monosaccharides.

[0022] The fermented solution can also comprise xylitol and fermentingcan also comprise reducing (converting) xylose in the processed solutionto fermented xylitol. The fermented xylitol can be treated to removeethanol by distillation and xylitol will remain as a bottom product(distilled xylitol). The xylitol as a bottom product can comprise agreater concentration of distilled xylitol by weight on dry substance(solids) basis than the fermented xylitol in the fermented solution.

[0023] The xylitol bottom product can also be separated to produce axylitol product and residue. The xylitol product can comprise a greaterconcentration of xylitol by weight on a dry substance (solids) basisthan the distilled xylitol in the xylitol bottom product Separation ofthe xylitol bottom product can be accomplished by chromatographicseparation, such as by: batch separation, continuous simulated movingbed separation, or sequential simulated moving bed separation.Separation of the xylitol bottom product can also be accomplished byfiltering, such as by: membrane filtration, ultrafiltration,nanofiltration, or microfiltration. The filtering can also comprisepassing the xylitol bottom product through at least one membrane, suchas: a high shear membrane, a vibrating membrane, a rotating membrane, aflat sheet membrane, a tubular membrane, a spiral membrane, a hollowfiber membrane, a neutral charged membrane, an ionic membrane, acationic membrane, or an anionic membrane.

[0024] Xylitol and xylitol product can be recovered either as a liquidxylitol or crystallized to produce xylitol crystals. Crystallization canbe accomplished by different methods, e.g. by cooling crystallizationThe xylitol crystals can be separated by centrifugation or filtrationand optionally washed with water to produce substantially purecrystalline xylitol.

[0025] The method can further include removing solids from the processedsolution. Furthermore, the method can include: separating a substantialportion of the spent microbes from the fermented solution prior to orafter distillation to produce fermented liquid derived from thefermented solution. The fermented liquid can comprise ethanol, as wellas substantially less spent microbes by weight on a dry substance(solids) basis than the spent microbes in the fermented solution. Asubstantial portion of the spent microbes can be separated from thefermented solution by filtration, centrifugation, and decanting.

[0026] Processing of the lignocellulose-containing material can furthercomprise at least one of the following: prehydrolysis of thelignocellulose-containing material, steam explosion of thelignocellulose-containing material, enzymatic hydrolysis of thelignocellulose-containing material with enzymes having a cellulolyticand hemicellulolytic e.g. xylanolytic activity to hydrolyze thelignocellulose-containing material, acid hydrolysis of thelignocellulose-containing material, chromatographic separation,ion-exchange purification, precipitation, partial hydrolysis of thelignocellulose-containing material, or extraction of thelignocellulose-containing material.

[0027] The prehydrolysis process can be performed by physical, chemical,or biological methods such as steam pretreatment, milling, steamexplosion, acid treatment (e.g. hydrochloric acid, phosphoric acid,sulfuric acid, sulfur dioxide), alkaline treatment (e.g. sodiumhydroxide, ammonia), or treatment with organic solvents (e.g. ethanol,ethylene glycol) or white rot fungi. In the prehydrolysis step, thehemicellulose can be liquefied which can sometimes result in a mixtureof monosaccharides and oligosaccharides.

[0028] The hydrolysis of the cellulose can be performed by weak acids orby enzymes. Concentrated hydrochloric acid or sulphuric acid can also beutilized. If desired, the prehydrolysis and hydrolysis can be carriedout in one step or two. Generally, acid hydrolysis procedures give riseto a broad range of compounds in the resulting hydrolysate, some ofwhich might negatively influence the subsequent steps in the process. Astrong and weak acid hydrolysis process can be combined with a weak acidprehydrolysis or alkaline treatment.

[0029] Processing can further comprise partially hydrolyzing thelignocellulose-containing material. The partially hydrolyzedlignocellulose-containing material can be separated into an extractedbiomass comprising hexosans as glucans and a prehydrolyzate comprisingfree hexoses and pentoses as xylose. The extracted biomass can behydrolyzed to produce a hydrolyzate comprising hexoses. Fermenting canfurther comprise: fermenting the hydrolyzate to produce a fermentedsolution comprising ethanol; and fermenting the prehydrolyzate toproduce a fermented solution comprising xylitol.

[0030] The method can further comprise post processing the processedsolution in at least one post processing step, such as: crystallization,chromatography, ion-exchange, concentration, evaporation, reverseosmosis, color removal e.g. by carbon or resin, reduction,detoxification, or catalytic hydrogenation. Furthermore, the processedsolution can be detoxified to help remove inhibitors prior to fermentingby one or more of the following: overliming, calcium hydroxide addition,hydroxide addition, pH adjustment, concentration e.g. by evaporation ,filtering, activated charcoal treatment, extraction with organicsolvents, ion exchange, ion exclusion, molecular sieves, steamstripping, heating, removing furfural, stripping volatile compounds, andreducing of the processed solution by sulphite addition.

[0031] The microbes used to ferment the processed solution can compriseat least one fermenting microorganism, such as: naturally occurringbacteria, recombinant bacteria, naturally occurring yeast, recombinantyeast, or fungi. The naturally occurring bacteria can comprise: Bacillusmacerans DMS 1574, Bacteroides polypragmatus NRCC 2288, Clostridiumsaccharolyticum ATCC 35040, C. thermohydrosulfurcium 39E, C.thermohydrosulfurcium ATCC 31925, Erwinia chrysanthemi 8374,Thermoanaerobacter ethanolicus ATTC 31938, Lactobacillus brevis, orLacococcus lactis ssp. Lactis. The recombinant bacteria can comprise:Erwinia chrysanthemi 8374, Escherichia coli B, E. coli B K011,Koebsiella oxytoca M5A1, K. planticola SDF20, Zymomonas mobilis CP4, orZ. mobilis NRRL 14023.

[0032] The naturally occurring yeast can comprise: Candida blanki ATCC18736, C. acidothermophilum ATCC 20831, C. brassicae ATCC 32196, C.famata, C. fructus JCM 1513, C. guilliermondii ATCC22017, C. shehataeCBS 4705, C. shehatae CSIR Y492, C. shehatae ATCC 22984. sp CSIR 62 A/2,C. tenius CBS 4435, C. tropicalis KY 5014, C. tropicalis ATCC 20240, C.tropicalis ATCC 9968, C. tropicalis NRRL y 11860, Clavispora sp. UWO83-833-1, Kluyveromyces cellobiovous KV 5199, K. marxianus, Pachysolentannophilus NRRL Y 2460, P. tannophilus RL 171, Pichia segobiensis CBS6857, P. stipitis CBS 5773, P. stipitis CBS 5776, P. stipitis NRRL Y1714, Schizosaccharomyces pombe ATCC 2478, Hansenula anomala ATCC 34080,Kluyveromyces fragilitis ATCC 12424, Saccharomyces uvarum ATCC 24556, S.uvarum ATCC 26602, F. oxysporum, or Debaryomyces hansenii.

[0033] The recombinant yeast can comprise Saaccharomyces cerevisiae, S.cerevisiae TJ1, S. cerevisiae H550, S. cerevisiae ATCC 24860,Schizosaccharomyces pombe ATCC 2456, or S. pombe NRRL Y164.

[0034] The filamentous fungi can comprise: Aeurobasidium pullulans,Fusarium avenaceium VTT-D-80146, F. clamydosporum VTT-D-77055, F.culmorum VTT-D-80148, F. graminearum VTT-D-79129, F. lycopersici ATCC15417, F. oxysporum VTT-D-80134, F. sembucium VTT-D-77056, F. solaniVTT-D-80139, Monilia sp., Mucor sp. 105, Neurospora crassa NCIM 870, orPaecilomyces sp. NFI ATCC 20766.

[0035] Preferably, the fermenting microorganism is a yeast of the generaCandida, Pichia, Pachysolen, or Debaryomyces, such as: Candidatropicalis, Candida tropicalis strain having an accession number ATCC9968, Pachysolen tannophilus, or Debaryomyces hansenii.

[0036] Fermenting can occur as continuous or batch fermentation at atemperature ranging from about 10 to about 45 degrees C. at a pH rangingfrom 4 to 7 with a yeast concentration of about 1 to about 40 g of dryyeast per liter of processed solution for about 24 to about 96 hours inthe presence of at least one nutrient. The nutrient can comprise: ayeast extract, diammoniumphosphate, peptone, biotin, thiamin, folicacid, a water soluble vitamin, a fat soluble vitamin, vitamin A, vitaminB complex, vitamin D, vitamin E, vitamin K, vitamin B1, vitamin B2,vitamin B5, vitamin B6, vitamin B12, vitamin B15, or another vitamin.

[0037] A more detailed explanation of the invention is provided in thefollowing description and appended claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038]FIG. 1 illustrates a graph of chromatographic separation;

[0039]FIG. 2 illustrates a process flow chart of one method of theinvention;

[0040]FIG. 3 illustrates a process flow chart of another method of theinvention;

[0041]FIG. 4 illustrates a process flow chart of a further method of theinvention;

[0042]FIG. 5 illustrates a process flow chart of still another method ofthe invention; and

[0043]FIG. 6 illustrates a process flow chart of still a further methodof the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0044] The following is a detailed description and explanation of thepreferred embodiments of the methods of the invention along with someexamples thereof.

[0045] It has now been found that xylitol and ethanol can be producedand recovered simultaneously by one of the processes of the inventionwherein xylose is mainly converted to xylitol but alternativelyconverted into ethanol while the majority of the hexoses present in theraw material are converted to ethanol. Thus the raw material iseffectively utilized and at least two commercially very importantproducts are obtained in a pure form and with a high yield. The processis beneficial and effective.

[0046] The process of the invention can be characterized in that thehydrolyzed starting material is fermented with a microbe e.g. yeaststrain, the ethanol produced is recovered, a separation is carried outon the remaining xylitol solution, and pure xylitol may be crystallized.Xylose-containing substances can be used as starting materials and canbe fermented with a yeast strain or other microbes that are capable ofconverting xylose to xylitol and/or ethanol and most hexoses to ethanol.By fermentation, a xylitol-rich solution is obtained wherefrom xylitolis recovered. Generally the xylitol can be purified, such as bychromatographically, membrane separation, etc., whereafter it can becrystallized to obtain pure xylitol. Ethanol can be removed from thefermentation solution such as by distillation . Therefore, the need forseparating xylitol from the hexitols and other sugars produced in thehydrolysis and reduction steps can be avoided to great extent.Advantageously, the hydrolysis performed in accordance with theinvention also provides a solution to the problem of using pulpdiscarded as waste mass in other processes, and thus in the process ofthe invention substantially the entire starting material is utilized.

[0047] Almost any xylan-containing material can be used as a startingmaterial in the process of the invention. Possible starting materialsinclude wood, softwood as pine and spruce, hardwood such as alder,aspen, birch, beech, maple, poplar, , eucalyptus, willow etc., andplants or plant constituents, grains as wheat, barley, rice, rye andoat, particulates of grain as straw, hulls, husks, fiber, shells, stemscorn cobs, corn straw, corn fiber, nutshells, almond shells, coconutshells, bagasse, and cottonseed bran, cottonseed skins. When wood isused as a starting material, it is advantageously comminuted or used aschips, sawdust, etc. and treated by hydrolysis or steam explosion andposthydrolysis, in which connection a carbohydrate material useful inthis invention is obtained.

[0048] In addition to the above, for instance by-products which areformed in processing and production of woodpulp and which have a highxylan or xylose content can be used. As an example may be mentioned theacid sulphite spent liquor produced in the manufacture of woodpulp bythe sulphite pulping process, said spent liquor containing smallquantities of undissolved wood solids, and soluble substances such aslignosulphonates, hexoses and pentoses, including xylose, and being agood raw material for use in the production of xylitol. Otherby-products and spent products produced in the processing of paper andwoodpulp, such as prehydrolysates from the production of dissolving pulpand spent liquor from the so called neutral sulphite pulping process,which have a high xylan and/or xylose content, can also be used.

[0049] The process of the invention can employ an aqueous solutioncontaining free xylose. Thus it may be necessary to carry out an acidand/or enzyme hydrolysis on the starting material to break down thexylan into xylose. Processes for hydrolyzing xylan-containing materialsto produce xylose-containing solutions have been described e.g. in U.S.Pat. Nos. 3,784,408 (Jaffe et al.) and 3,586,537 (Steiner et al.).

[0050] The starting material may, if desired, be pretreated before thefermentation to remove constituents which may be toxic or otherwisedisadvantageous to the yeast or other microbes. The necessity of thepretreatment step is dependent on the starting material used and theyeast or other microbes used in the fermentation step. The pretreatmentof the starting material may include for instance posthydrolysis,chromatographic separation, ion exchange purification, precipitation,steam stripping etc.

[0051] One method of the invention is illustrated in the process flowchart of FIG. 2.

[0052] The hydrolysis can comprise two steps, prehydrolysis of thecellulose-containing raw material, which may be effected using the socalled steam explosion method, weak acid hydrolysis and the enzymatichydrolysis of the polysaccharides and oligosaccharides to produce thecorresponding monosaccharides. This step can be carried out usingenzymes which have a high cellulolytic and xylanolytic activity.

[0053] The remaining solids, consisting for the most part of lignin andcellulose, can be then separated from the solution obtained.Alternatively, the solids and the solids produced in the fermentation,such as spent yeast or other spent microbes, can be separated orcollected before or after the next distillation.

[0054] When relatively impure solutions are used as a starting material,pretreatment of the solutions may be necessary in some cases. Thepretreatment may be e.g. posthydrolysis and/or separation of theconstituents which may be toxic and/or disadvantageous to the yeastemployed or which have an adverse effect on the fermentation orseparation steps. The pretreatment may also be combined withchromatographic separation, ion exchange purification, precipitation,etc.

[0055] Thereafter, the solution can be fermented with a suitable yeaststrain or other microbes. One embodiment of the invention employs yeaststhat are capable of reducing xylose into xylitol and hexoses intoethanol and/or use hexoses for their growth. Such yeasts are forinstance yeasts of the genera Candida, Pichia, Pachysolen, mutatedSaccharomyces, Debaryomyces. Candida and Debaryomyces species,particularly Candida tropicalis and Debaryomyces hansenii, are regardedas advantageous. As a good example may be mentioned the Candidatropicalis strain deposited at the American Type Culture Collectionunder the accession number ATCC 9968. The xylose content of the aqueoussolution to be fermented is dependent on the starting material andprocess steps employed, but is advantageously about 50-300 g/l.

[0056] The fermentation can be carried out in most commerciallyavailable fermentors which are furnished with aerating means andstirring and pH regulating means. The temperature is advantageouslyabout 20-40 degrees C., most advantageously about 30 degrees C. Theyeast cells are added to the xylose-rich solution. Generally, it can besaid that the higher the yeast concentration, the faster thefermentation step is. It has been found that the yeast concentration isadvantageously about 1-20 g ( up to 30-50g) of dry yeast/l of substrate(dry weight) when the xylose content is about 50-300 g/l.

[0057] The fermentation can be enhanced by adding nutrients, as in onebatch, until the most part of the xylose has been converted to xylitoland substantially all hexoses have been converted to ethanol and/or usedfor yeast growth. The fermentation generally takes about 24-144 hours,preferably 24-72 hours. With the process of the invention, up to 90% ofthe xylose can be converted to xylitol and part to ethanol.

[0058] After the fermentation step, the solution can be clarified priorto the separation of xylitol and ethanol therefrom. The spent yeastcells or other spent microbes can be removed after the fermentation.This may be carried out by centrifugation, filtration, decanting or someother procedure. When the spent yeast cells or other spent microbes havebeen removed and the solution is clear, the ethanol produced in thefermentation can be recovered by evaporation, distillation or some otherprocedure. Alternatively, the removal of the spent yeast cells or otherspent microbes can be carried out after the distillation.

[0059] To recover xylitol, chromatographic separation can be firstperformed. This is advantageously carried out in a column filled with asulphonated polystyrene resin cross-linked with divinylbenzene in thealkaline-earth or alkali metal form. A large-scale chromatographicmethod suitable for this purpose has been described in U.S. Pat. No.3,928,193 (Melaja et al.). The chromatographic separation can also becarried out using a simulated moving bed, such as described in U.S. Pat.No. 2,985,589.

[0060] From the fraction having a high xylitol content obtained from thechromatographic step or after additional purification, xylitol can becrystallized with a good yield using conventional crystallizationmethods, such as cooling crystallization . When cooling crystallizationis used, xylitol crystals of an average diameter of about 30 μm areadded as seed crystals to the concentrated xylitol solution, whereafterthe temperature of the solution can be slowly decreased. The crystalsobtained, the average diameter of which is about 250-600 μm, can beseparated for instance by centrifugation or filtration and washed withwater to obtain substantially pure crystalline xylitol.

[0061] The process can also be carried out in a preferable alternativeway so that the starting material is subjected to partial hydrolysis andextraction. The prehydrolysate obtained from the extraction can thenfermented to convert xylose to xylitol, which can be separatedchromatographically and crystallized in the above-stated manner. A finalhydrolysis can be carried out on the extracted mass, the hydrolysisproduct can be fermented to convert hexoses to ethanol, and ethanol canbe recovered in the manner described above or using other methods asmembrane process, pervaporation or reverse osmosis.

[0062] Other methods of the invention are illustrated in the processflow charts of FIGS. 3-6 and/or are described in the specification ofthis application.

[0063] In one method, lignocellulose-containing material fromxylan-containing matter in biomass comprising pentoses and hexoses ishydrolyzed to produce a hydrolyzed solution comprising free pentoses andhexoses. The hydrolyzed solution can be fermented with microbes toproduce a fermented solution comprising fermented ethanol, fermentedxylitol-producing solution, fermented xylose, and spent microbes. Duringfermentation a substantial amount of the hexose in the hydrolyzedsolution can be converted to fermented ethanol. Also, duringfermentation a substantial amount of the pentose in the hydrolyzedsolution can be reduced to fermented xylitol solution, fermented xyloseand fermented ethanol.

[0064] Fermented liquid derived from the fermented solution can bedistilled to produce distilled ethanol and a distilled solutioncomprising distilled xylitol solution, distilled xylose and spentmicrobes. The distilled ethanol can comprise a greater concentration ofethanol by weight on a liquid basis than the fermented ethanol in thefermented solution. The bottom product can also have a greaterconcentration of distilled xylitol-producing solution by weight on a drysubstance (solids) basis than the fermented xylitol-producing solutionin the fermented solution.

[0065] The bottom product can be separated by fractionating thedistilled solution into fractions comprising a separatedxylitol-producing fraction and a separated xylose fraction. Theseparated xylitol-producing fraction can comprise a greaterconcentration of xylitol-producing solution by weight on a dry substance(solids) basis than the distilled xylitol-producing solution in thedistilled solution.

[0066] The hydrolyzed solution can be post treated by one or more of thefollowing: pH adjustment, concentration, filtration, filtering with apressure filter, filtering with diatomaceous earth, chromatographicseparation, detoxification, removing inhibitors, liming, calciumhydroxide addition, calcium oxide addition, sodium hydroxide addition,activated charcoal treatment, extraction with organic solvents, ionexchange, ion exclusion, treatment with molecular sieves, steamstripping, heating, removing furfural, stripping volatile compounds, andreduction of the hydrolyzed solution by sulphite addition.Advantageously, the xylitol-producing solution has a greaterconcentration of at least one compound, such as xylitol, xylose,arabinose, mannose, or galactose and rhamnose, on a dry substance(solids) basis than the compound in the hydrolyzed solution.

[0067] The distilled solution can be separated by chromatographicseparation, such as by: batch separation, continuous simulated movingbed separation, or sequential simulated moving bed separation. Thedistilled solution can also be separated by filtering, such as by:membrane filtration, ultrafiltration, nanofiltration, ormicrofiltration. The filtering can comprise passing the xylitol bottomproduct through at least one membrane, such as: a high shear membrane, avibrating membrane, a rotating membrane, a flat sheet membrane, atubular membrane, a spiral membrane, a hollow fiber membrane, a neutralcharged membrane, an ionic membrane, a cationic membrane, or an anionicmembrane.

[0068] The process can further include: hydrogenating thexylitol-producing fraction to produce hydrogenated xylitol, and/orhydrogenating of the separated xylose fraction to produce hydrogenatedxylitol.

[0069] The xylitol fraction and/or hydrogenated xylitol can becrystallized to produce xylitol crystals. Crystallization can beaccomplished by different methods, such as: cooling crystallization orevaporation crystallization or both or combination. The xylitol crystalscan be separated e.g. by centrifugation and filtration and optionallywashed with water to produce substantially pure crystalline xylitol.

[0070] The method can also include separating a substantial portion ofthe spent microbes from the fermented solution prior to the distillingto produce fermented liquid derived from the fermented solution. Suchseparation (clarification) can be accomplished by: filtration,centrifugation, flocculation, flotation and decanting. The fermentedliquid can comprise: fermented ethanol, fermented xylitol, fermentedxylose, and spent microbes. The fermented liquid can desirably comprisesubstantially less spent microbes by weight on a dry substance (solids)basis that the spent microbes in the fermented solution. A substantialamount of solids from the hydrolyzed solution can further be removedbefore fermenting, by at least one removal step, such as by: filtration,centrifugation, decanting and clarification using flocculation.

[0071] Hydrolyzing of the lignocellulose-containing material can beaccomplished by enzymatic hydrolysis of the lignocellulose-containingmaterial with enzymes having a cellulolytic and xylanolytic activity tohydrolyze the lignocellulose-containing material, or by acid hydrolysisof the lignocellulose-containing material.

[0072] The lignocellulose-containing material can also be pretreatedbefore hydrolyzing. Such pretreatment can comprise at least onepretreatment method, such as: prehydrolysis of thelignocellulose-containing material, steam explosion of thelignocellulose-containing material, alkaline treatment, solventextraction, partial hydrolysis of the lignocellulose-containingmaterial, and extraction of the lignocellulose-containing material.

[0073] The lignocellulose-containing material can comprise at least onelignocellulosic material, such as cellulose, hemicellulose, or lignin.The xylan-containing matter can comprise one or more of the following:wood, hardwood as alder, aspen, birch, beech, eucalyptus, poplar,willow, softwood as pine and spruce, plants, plant constituents, grainas wheat, barley, rye, rice and oat, particulates of grain as straw,hulls, husks, fiber, stems, shells, corn cobs, cornstraw, corn fiber,nutshells, almond shells, coconut shells, bagasse, cotton seed bran,cotton seed skins, wood chips, sawdust, woodpulp, processed paper, spentsulphite liquor, spent liquor from paper processing, spent liquor fromwoodpulp processing, sulphite cooking liquor, or liquids derived fromany of the preceding.

[0074] The hydrolyzed solution can comprise biomass hydrolysates. Thebiomas hydrolysates can be obtained by: direct acid hydrolysis of thebiomass, enzymatic prehydrolysate obtained by prehydrolysis of thebiomass with steam or acetic acid, acid hydrolysis of prehydrolysateobtained by prehydrolysis of the biomass with steam or acetic acid, or asulphite pulping process. The biomass hydrolysates can also comprise orbe derived from: spent sulphite pulping liquor, acid spent sulphiteliquor, spent liquor from softwood pulping before hexoses are removed,spent liquor from softwood pulping after hexoses are removed, spentliquor from hardwood pulping, spent liquor from digestion of thebiomass, spent liquor from hydrolysis of the biomass, spent liquor fromsolvent-based pulping, spent liquor from phenol based pulping, spentliquor from formic acid based pulping, spent liquor from ethanol-basedpulping, mother liquor from crystallization of xylose, and dilutedrunoff of xylose crystallization of sulphite spent pulping liquor basedfraction.

[0075] The pentose can comprise at least one pentose-containingmaterial, such as xylose or arabinose. During fermentation, arabinose inthe processed solution can be reduced to arabinitol. The hexose cancomprise at least one hexose-containing material, such as: glucose,galactose, rhamnose, mannose, or other monosaccharides.

[0076] The microbes used to ferment the hydrolyzed solution can compriseat least one fermenting microorganism, such as: naturally occurringbacteria, recombinant bacteria, naturally occurring yeast, recombinantyeast, or fungi. The naturally occurring bacteria can comprise: Bacillusmacerans DMS 1574, Bacteroides polypragmatus NRCC 2288, Clostridiumsaccharolyticum ATCC 35040, C. thermohydrosulfurcium 39E, C.thermohydrosulfurcium ATCC 31925, Erwinia chrysanthemi 8374,Thermoanaerobacter ethanolicus ATTC 31938, Lactobacillus brevis, orLacococcus lactis ssp. Lactis. The recombinant bacteria can comprise:Erwinia chrysanthemi 8374, Escherichia coli B, E. coli B K011,Kiebsielle oxytoca M5A1, K. planticolsa SDF20, Zymomonas mobilis CP4, orZ. mobilis NRRL 14023.

[0077] The naturally occurring yeast can comprise: Candida blanki ATCC18736, C. acidothermophilum ATCC 20831, C. brassicae ATCC 32196, C.famata, C. fructus JCM 1513, C. guiuilliermondii ATCC22017, C. shehataeCBS 4705, C. shehatae CSIR Y492, C. shehatae ATCC 22984. sp CSIR 62 A/2,C. tenius CBS 4435, C. tropicalis KY 5014, C. tropicalis ATCC 20240, C.tropicalis ATCC 9968, C. tropicalis NRRL y 11860, Clavispora sp. UWO83-833-1, Kluyveromyces cellobiovous KV 5199, K. marxianus, Pachysolentannophilus NRRL Y 2460, P. tannophilus RL 171, Pichia segobiensis CBS6857, P. stipitis CBS 5773, P. stipitis CBS 5776, P. stipitis NRRL Y1714, Schizosaccharomyces pombe ATCC 2478, Hansenula anomala ATCC 34080,Kluyveromyces fragilitis ATCC 12424, Saccharomyces uvarum ATCC 24556, S.uvarum ATCC 26602, F. oxysporum, or Debaryomyces hansenii. Therecombinant yeast can comprise Saccharomyces cerevisiae, S. cerevisiaeTJ1, S. cerevisiae H550, S. cerevisiae ATCC 24860, Schizosaccharomycespombe ATCC 2456, or S. pombe NRRL Y164.

[0078] The fungi can comprise: Aureobasidium pullulans, Fusariumavenaceium VTT-D-80146, F. clamydosporum VTT-D-77055, F. culmorumVTT-D-80148, F. graminearum VTT-D-79129, F. lycopersici ATCC 15417, F.oxysporum VTT-D-80134, F. sembucium VTT-D-77056, F. solani VTT-D-80139,Monilia sp., Mucor sp. 105, Neurospora crassa NCIM 870, or Paeceilmycessp. NFI ATCC 20766.

[0079] Preferably, the fermenting microorganism is a yeast of the generaCandida, Pichia, Pachysolen, or Debaryomyces, such as: Candidatropicalis, Candida tropicalis strain having an accession number ATCC9968, Pachysolen tannophilus, or Debaryomyces hansenii.

[0080] Fermenting can occur at a temperature ranging from about 10 toabout 45 degrees C. at a pH ranging from 4 to 7 with a yeastconcentration of about 1 to about 40 g of dry yeast per liter ofprocessed solution for about 24 to about 96 hours in the presence of atleast one nutrient. The nutrient can comprise: a yeast extract,diammoniumphosphate, peptone, biotin, thiamin, folic acid, a watersoluble vitamin, a fat soluble vitamin, vitamin A, vitamin B complex,vitamin D, vitamin E, vitamin K, vitamin B1, vitamin B2, vitamin B5,vitamin B6, vitamin B12, vitamin B15, or another vitamin.

[0081] Another method of processing lignocellulose-containing materialfrom xylan-containing matter in biomass comprising pentose and hexose,can comprise partially hydrolyzing the lignocellulose-containingmaterial from xylan-containing matter in biomass comprising pentose andhexose to produce a partially hydrolyzed solution comprising freepentoses and hexoses, pentosans, and hexosans. The partially hydrolyzedsolution can be separated into an extracted biomass and solubles, theextracted mass comprising hexosans as glucans, and solids as lignin andcellulose, the solubles comprising pentoses, hexoses, soluble pentosansand hexosans, and residue.

[0082] The extracted biomass can be hydrolyzed to produce a hydrolyzedbiomass comprising hydrolyzed hexoses, hydrolyzed pentoses, andhydrolyzed solids. During hydrolysis, a substantial amount of thepentosans can be converted to pentoses, and a substantial amount of thehexosans can be converted to hexoses. The hydrolyzed biomass can beseparated into solids comprising lignin and a separated biomass solutioncomprising pentoses and hexoses. The separated biomass solution cancomprise a greater concentration of pentoses by weight on a drysubstance (solids) basis than the hydrolyzed pentoses in the hydrolyzedbiomass. Furthermore, the separated biomass solution can comprise agreater concentration of hexoses by weight on a dry substance (solids)basis than the hydrolyzed hexoses in the hydrolyzed biomass. Also, theseparated biomass can comprise a greater concentration of solids byweight on a dry substance (solids) basis than the hydrolyzed solids inthe hydrolyzed biomass.

[0083] The solubles can be fractionated to separate the solubles intofractions comprising a xylose-rich fraction, a xylose-containingfraction, a recycle fraction, and a residue (residual) fraction. Thexylose-rich fraction can comprise a higher concentration of xylose byweight on a dry substance (solids) than the xylose in the solubles. Theresidue fraction can comprise a higher concentration of residue byweight on a dry substance (solids) than the residue in the solubles.Furthermore, the xylose-rich fraction can comprise a higherconcentration of at least one compound, such as consisting of xylose,arabinose, mannose, or galactose and rhamnose, by weight on a drysubstance (solids) than the compound in the other fractions.

[0084] The xylose-rich fraction can be reduced, such as by chemicalhydrogenation or biochemical hydrogenation, to produce reduced xylitol.Before reduction xylose fraction can be purified e.g. ion exchange. Thehydrogenated xylitol can have a greater concentration of xylitol byweight on a dry substance (solids) basis than the xylitols in thesolubles.

[0085] The xylose-containing fraction and the separated biomass solutioncan be fermented with microbes to produce a fermented solutioncomprising fermented ethanol and spent microbes. During fermentation ofthe xylose-containing fraction and the separated biomass solution, asubstantial amount of the xylose in the xylose-containing fraction canbe reduced to fermented ethanol and/or xylitol and/or a substantialamount of the pentoses and hexoses in the separated biomass solution canbe converted to fermented ethanol. Arabinose in the separated biomasscan be reduced to arabinitol during fermentation. Fermented liquidderived from the fermented solution can be distilled to produce adistilled solution comprising distilled ethanol. The distilled ethanolcan comprise a greater concentration of ethanol by weight on a liquidbasis than the fermented ethanol in the fermented solution.

[0086] A substantial portion of the spent microbes from the fermentedsolution can be separated, such as by filtration, centrifugation, anddecanting, prior to the distilling to produce the fermented liquidderived from the fermented solution. The fermented liquid can comprisefermented ethanol and some spent microbes. The fermented liquid cancomprise substantially less spent microbes by weight on a dry substance(solids) basis that the spent microbes in the fermented solution.

[0087] Separation of the hydrolyzed biomass can be accomplished by atleast one separation method, such as: filtration of the hydrolyzedbiomass, membrane filtration of the hydrolyzed biomass, ultrafiltrationof the hydrolyzed biomass, nanofiltration of the hydrolyzed biomass,microfiltration of the hydrolyzed biomass, centrifugation of thehydrolyzed biomass, decanting of the hydrolyzed biomass, crystallizationof the hydrolyzed biomass, chromatography, ion-exchange of thehydrolyzed biomass, concentration of the hydrolyzed biomass, evaporationof the hydrolyzed biomass, reverse osmosis of the hydrolyzed biomass,color removal of the hydrolyzed biomass, reduction of the hydrolyzedbiomass, detoxification of the hydrolyzed biomass, and catalytichydrogenation of the hydrolyzed biomass.

[0088] The separated biomass solution and/or the xylose-containingfraction, can be detoxified to help remove inhibitors prior tofermenting with one or more of the following: liming, calcium hydroxideaddition, calcium oxide addition, sodium hydroxide addition, pHadjustment, activated charcoal treatment, extraction with organicsolvents, ion exchange, ion exclusion, molecular sieves, steamstripping, heating, removing furfural, stripping volatile compounds, andreduction of the separated biomass solution by sulphite addition.

[0089] If desired, at least some of the solids in the extracted biomasscan be burned (combusted or incinerated). Residue after total hydrolysiscontaining lignin can be used as binder or disintegrant.

[0090] The solubles can be fractionated by chromatographic separation,such as by: batch separation, continuous simulated moving bedseparation, or sequential simulated moving bed separation. The solublescan also be fractionated by filtering the solubles, such as by: membranefiltration, ultrafiltration, nanofiltration, or microfiltration.Filtering can comprise passing a solution comprising the solublesthrough at least one membrane, such as: a high shear membrane, avibrating membrane, a rotating membrane, a flat sheet membrane, atubular membrane, a spiral membrane, a hollow fiber membrane, a neutralcharged membrane, an ionic membrane, a cationic membrane, and an anionicmembrane.

[0091] The hydrogenated fraction can be crystallized to produce xylitolcrystals. Crystallization can be accomplished by different methods, e.g.cooling crystallization The xylitol crystals can be separated e.g. bycentrifugation or filtration and washed with water to producesubstantially pure crystalline xylitol.

[0092] Hydrolysis of the extracted biomass can be accomplished byenzymes having a cellulolytic and hemicellulolytic e.g. xylanolyticactivity to hydrolyze the extracted biomass, or acid hydrolysis of theextracted biomass or by autohydrolysis using water or steam.

[0093] Partially hydrolyzing of the lignocellulose-containing materialcan be accomplished by: steam explosion of the lignocellulose-containingmaterial, partial enzymatic hydrolysis of the lignocellulose-containingmaterial with enzymes having a cellulolytic and hemicellulolytic e.g.xylanolytic activity to partially hydrolyze thelignocellulose-containing material, and partial acid hydrolysis of thelignocellulose-containing material, or subjecting thelignocellulose-containing material to acetic acid.

[0094] The partially hydrolyzed solution can be separated and/orclarified by at least one separation method selected form the groupconsisting of: centrifugation of the partially hydrolyzed solution,decanting of the partially hydrolyzed solution, crystallization of thepartially hydrolyzed solution, precipitation as CaSO ₄-precipitation,chromatography of the partially hydrolyzed solution, ion-exchange,concentration of the partially hydrolyzed solution, evaporation of thepartially hydrolyzed solution, reverse osmosis of the partiallyhydrolyzed solution, filtration of the partially hydrolyzed solution,membrane filtration of the partially hydrolyzed solution,ultrafiltration of the partially hydrolyzed solution, nanofiltration ofthe partially hydrolyzed solution, or microfiltration of the partiallyhydrolyzed solution.

[0095] As previously indicated, the partially hydrolyzed solution cancomprise biomass hydrolysates. The biomass hydrolysates can comprise:spent sulphite pulping liquor, acid spent sulphite liquor, spent liquorfrom hard wood pulping, spent liquor from softwood pulping beforehexoses are removed, spent liquor from softwood pulping after hexosesare removed, spent liquor from digestion of the biomass, spent liquorfrom hydrolysis of the biomass, spent liquor from solvent-based pulping,spent liquor from phenol based pulping, spent liquor from formic acidbased pulping, spent liquor from ethanol-based pulping, mother liquorfrom crystallization of xylose, and diluted runoff of xylosecrystallization of sulphite spent pulping liquor based liquor.

[0096] The microbes used to ferment the xylose-containing fraction andthe separated biomass solution can comprise at least one fermentingmicroorganism, such as: naturally occurring bacteria, recombinantbacteria, naturally occurring yeasts, recombinant yeasts, or filamentousfungi. As previously indicated, the naturally occurring bacteria cancomprise: Bacillus macerans DMS 1574, Bacteroides polypragmatus NRCC2288, Clostridium saccharolyticum ATCC 35040, C. thermohydrosulfrurcium39E, C. thermohydrosulfuricum ATCC 31925, Erwinia chrysanthemi 8374,Thermoanaerobacter ethanolicus ATTC 31938, Lactobacillus brevis, orLacococcus lactis ssp. Lactis. The recombinant bacteria can comprise:Erwinia chrysanthemi 8374, Escherichia coli B, E. coli B K011,Klebsiella oxytoca M5A1, K. planticola SDF20, Zymomonas mobilis CP4, orZ. mobilis NRRL 14023. The naturally occurring yeasts can comprise:Candida blanki ATCC 18736, C. acidothermophilum ATCC 20831, C. brassicaeATCC 32196, C. famata, C. fructus JCM 1513, C. guilliermondii ATCC22017,C. shehatae CBS 4705, C. shehatae CSIR Y492, C. shehatae ATCC 22984. spCSIR 62 A/2, C. tenuis CBS 4435, C. tropicalis KY 5014, C. tropicalisATCC 20240, C. tropicalis ATCC 9968, C. tropicalis NRRL y 11860,Clavispora sp. UWO 83-833-1, Kluyveromyces cellobiovous KV 5199, K.marxianus, Pachysolen tannophilus NRRL Y 2460, P. tannophilus RL 171,Pichia segobiensis CBS 6857, P. stipitis CBS 5773, P. stipitis CBS 5776,P. stipitis NRRL Y 1714, Schizosaccharomyces pombe ATCC 2478, Hansenulaanomala ATCC 34080, Kluyveromyces fragilis ATCC 12424, Saccharomycesuvarum ATCC 24556, S. uvarum ATCC 26602, F. oxysporum, or Debaryomyceshansenii. The recombinant yeast can comprise: Saccharomyces cerevisiae,S. cerevisiae TJ1, S. cerevisiae H550, S. cerevisiae ATCC 24860,Schizosaccharomyces pombe ATCC 2456, or S. pombe NRRL Y164. The fungican comprise: Aureobasidium pullulans, Fusarium avenaceium VTT-D-80146,F. clamydosporum VTT-D-77055, F. culmorum VTT-D-80148, F. graminearumVTT-D-79129, F. lycopersici ATCC 15417, F. oxysporum VTT-D-80134, F.sembucium VTT-D-77056, F. solani VTT-D-80139, Monilia sp., Mucor sp.105, Neurospora crassa NCIM 870, or Paecilomyces sp. NFI ATCC 20766.

[0097] Preferably, the microbes used to ferment the xylose-containingfraction and the separated biomass solution is a yeast of the generaCandida, Pichia, Pachysolen, or Debaryomyces, such as: Candidatropicalis, Candida tropicalis strain having an accession number ATCC9968, Pachysolen tannophilus, or Debaryomyces hansenii.

[0098] Fermentation of the xylose-containing fraction and the separatedbiomass solution can occur at a temperature ranging from about 10 toabout 45 degrees C. at a pH ranging from 4 to 7 with a yeastconcentration of about 1 to about 40 g of dry yeast per liter ofsolution comprising the xylose-containing fraction and the separatedbiomass solution, for about 24 to about 96 hours in the presence of atleast one nutrient. The nutrient can comprise: a yeast extract,diammoniumphosphate, peptone, biotin, thiamin, folic acid, a watersoluble vitamin, a fat soluble vitamin, vitamin A, vitamin B complex,vitamin D, vitamin E, vitamin K, vitamin B1, vitamin B2, vitamin B5,vitamin B6, vitamin B12, vitamin B15, or another vitamin.

[0099] Different methods of detoxification, i.e., the removal ofinhibitors from xylose containing fraction can increase theirfermentability. The addition of activated charcoal, extraction withorganic solvents, ion-exchange, ion exclusion, molecular sieves, liming,and/or steam stripping, can be used to remove inhibitors. Liming canalso be used as a detoxification method and can be implemented invarious ways. Calcium hydroxide or some other hydroxide can be added tothe medium until the pH reaches 8.5-10.5. After mixing, the resultingprecipitate can be removed. The precipitate can comprise mainly calciumsalts of low solubility dominated by calcium sulfate or organic orinorganic anions This treatment can be combined with heat, because atelevated temperatures the solubility of calcium sulfate decreases.Volatile compounds, such as furfural, can be stripped off. Calciumsulfate precipitates acidic compounds. Sulfite is often added at somestage of the detoxification before or after overliming. Sulfitefunctions as a reducing agent.

[0100] The invention is described in further detail by means of thefollowing examples, which are not intended to restrict the invention.

EXAMPLE 1 Production of Ethanol and Xylitol from Birch Chip

[0101] A steam explosion treatment was carried out on birch chips at 215degrees C. with a delay time of 4.5 minutes. The apparatus used iscommercially available (Stake Technology, Canada).

[0102] 30 kg of chips pretreated by steam explosion were suspended in400 1 of water at 50 degrees C. in a reactor furnished with stirringmeans. The pH of the suspension was regulated to 4.8 with a NaOHsolution. The following enzymes were added into the reactor: CellulaseMultifect ® L 250 4 FPU/g d.s. (cultor) Beta-Glucosidase Novozyme ™ 1885 IU/g d.s. (Novo) Hemicellulase Multifect ® K (Cultor), containingxylanase 18 U/9 d.s. 6-xvlosidase 9 nkat/g d.s. esterase 2 nkat/g d.s.

[0103] The reaction was started, and after three and six hourspretreated birch chips were added to the mixture to increase the solidscontent to 14% by weight. The hydrolysis was continued for three days at50 degrees C. and at a pH of 4.8. The yield after the hydrolysis was 16%of glucose and 12% of xylose on the dry weight of the pretreated chips.

[0104] The solution was separated from the dry solids in a decantingcentrifuge (Sharples P 600). The finely powdered matter was removed in aWestfalia Na7-06-076 separator, and the xylose-glucose solution wasconcentrated by evaporation. The pH of the concentrate was 5.1, and thecomposition are shown in Table 1: TABLE 1 Glucose 10.3%  Xylose 7.6%Other monosacchariles 3.1% Oligosaccharides 5.5%

[0105] The total solids content was about 32%.

[0106] The solution additionally contained salts of organic acids andsmall amounts of lignin decomposition products, furfural, phenols andother organic substances.

[0107] The hydrolyzed product was fermented with the yeast Candidatropicalis ATCC 9968. A New Brunswick Scientific Co If 250 fermentor wasused, whereto gas analysis and mass spectrometric apparatus wasconnected.

[0108] The fermentation solution is shown in Table 2: TABLE 2 601prehydrolysate (dry solids content about 32%) 1.5 kg Gistex yeastextract (steam sterilized at 121 degrees C., 15 min.) 29 1 water

[0109] The inoculation cultures were grown in two stages, first in a 2 lErlenmeyer flask in an Orbital Shaker at 30 degrees C. for 2 days, andthen in a Microgen TM SF 116 laboratory fermentor having an operatingvolume of 11 l . The fermentor was aerated at a rate of 5.5 NI/min. (0.5VVM) and stirred at a rate of 500 rpm. The culturing lasted for one day.

[0110] The actual fermentation was performed on a pilot scale, theoperating volume being 100 l . The fermentor was aerated at a rate of 20N1/min. (0.2 VVM) and stirred at a rate of 100 rpm. The temperature wasmaintained at 30 degrees C. and the pH at 6. Plurior® was used as anantifoaming agent.

[0111] The fermentation results are shown in Table 3. TABLE 3 Time (h)Yeast (g/kg) Xylitol (g/l) Glucose (g/l) Ethanol (g/l) 0 2.0 0.0 53.51.9 16 6.1 2.9 2.4 26.4 23.5 4.7 26.7 41.0 7.4 9.0 1.9 25.6 65.0 8.015.8 24.9 91.5 6.1 21.2 23.4 136 20.6 22.3

[0112] After the fermentation, substantially all sugars had convertedinto xylitol and ethanol.

[0113] Ethanol was recovered from the solution by distilling thefermented solution in a conventional manner. The distillation apparatuswas constructed of standard components (Coming Process Systems) whichwere of borosilicate glass, and the apparatus comprised equipment for 15separation steps as follows: boiler, 13 bubble plates and a feed platebetween the fourth and fifth bubble plates seen from the top. Thediameter of the column was 10 cm.

[0114] The distillation was carried out at a pressure of 110 mbar at afeed rate of 10 l/h and with a reflux ratio of 3:1. 110 l of fermentingsolution gave 7.0 kg of distillate which contained 27. 1% by weight ofethanol. The ethanol content of the bottom product was 0.02% by weight.

[0115] The separation and, if desired, crystallization of xylitol werecarried out as described in Examples 2 and 3.

EXAMPLE 2 Production of Ethanol and Xylitol from Sulphite Spent Liquor

[0116] The starting material used was a sugar fractionchromatographically separated from a sulphite spent liquor (FinnishPatent Application 862273, U.S. Pat. No. 4,631,129), containing aconsiderable amount of hexoses, mainly glucose. The composition of thesolution prior and subsequent to fermentation is shown in Table 4. TABLE4 Before after ingredient fermentation fermentation dry solids, % byweight 19.0 — oligosacch., % of dry 14.8 10.3 solids glucose 90.0 1.4xylose 42.0 3.5 arabinose 5.0 2.3 xylitol — 25.4 ethanol 42.0 arabinitol2.8

[0117] The fermentation was carried out with a Debaryomyces hanseniistrain, and 3 g/l of yeast extract, 3 g/l of malt extract and 5 g/l ofpeptone were added. The pH of the solution to be fermented was initiallyabout 6.0, the temperature was about 30 degrees C. and the fermentationwas carried out in an Orbital Shaker (200 rpm).

[0118] The ethanol produced in the fermentation was recovered bydistillation (50 degrees C., 200 mbar), and a chromatographic separationwas carried out on the remaining solution in a column filled with adivinylbenzene-cross-linked polystyrene-based cation exchange resin, inwhich connection the conditions shown in Table 5 were used. TABLE 5height of column 4.0 m Diameter of column 22.5 cm temperature 65 ° C.flowrate (H 2 O) 30 1/h feed concentration 30 % by weight feed volume 6kg of solid matter resin: ^(Finex 198) C 09 Particle size 0.37 MM ionicform Na

[0119] The results have been graphically presented in FIG. 1. Xylitolwas separated from xylose and the other impurities, and recovered fromthe xylitol-rich fraction, wherefrom pure xylitol was crystallized inthe manner described in Example 3.

EXAMPLE 3 Crystallization of Xylitol

[0120] Xylitol was crystallized from a chromatographically enrichedxylitol solution containing 82.5% of xylitol on dry solids byevaporating the solution to 92% by weight of dry solids at 65 degrees C.Into a solution of a natural weight of 2,200 g, xylitol crystals ofabout 0.04 mm were inoculated in an amount of 0.03% by weight, and thesolution was cooled in 55 hours to 45 degrees C. in accordance with thefollowing empirical equation:

T=T 1−(t/t 1)**2*(T 1−T 2),

[0121] wherein

[0122] T=temperature of solution, degrees C.

[0123] T1=seeding temperature (65 degrees C.)

[0124] T2=final temperature (45 degrees C.)

[0125] t=time from seeding, h

[0126] t1=crystallization time (55 h)

[0127] The crystallization was carried out in a 2 l pilot crystallizerfurnished with a vertical stirrer. 65% of the xylitol present in thesolution crystallized as raw crystals which were separated from themother solution in a basket centrifuge (Hettich, Roto Silenta TM 11).

[0128] During the centrifugation, the crystals were washed with water(4% of water on the weight of the crystals). The centrifugation time was5 minutes, and a centrifugal force of 2000 g was used. 1,510 g ofnatural weight of a crystal suspension was centrifuged, which gave 705 gof crystalline dry solids having a xylitol content of 99.4% of drysolids. The average size of the crystals was 0.37 mm and the standarddeviation 24%.

[0129] The raw crystals can be recrystallized, into product crystals bye.g. the method disclosed in Finnish Patent No. 69 296.

EXAMPLE 4 Production of Ethanol and Xylitol from Barley Hulls

[0130] Barley hull mass having the carbohydrate composition in Table 6was used as a starting material. TABLE 6 xylan 21.6% of dry solidsglucan 33.4 araban  5.7 galactan  1.4 mannan  0.6 rhamnan  0.2

[0131] The barley hull mass was hydrolyzed at a pressure of 2.4 MPa (350psi) at 235 degrees C., and the delay time was 2.0 minutes. Thehydrolyzed material contained 45.6% of dry solids, and the content ofdissolved solids was 34.2% on dry solids. The filtrate contained 12.7%of monosaccharides, 16.9% of acetic acid and 0.5% of furfural calculatedon a dry solids basis. Posthydrolysis was carried out on the filtrate byadjusting the pH to 1 with sulphuric acid and by hydrolyzing thesolution for 4 hours at a pressure of 101 kPa (one atmosphere) at 100degrees C. The composition of the posthydrolysate is shown in Table 7.TABLE 7 oligosacoharides 1.39% of dry solids monosaccharides 45.2%xylose 67.3% of the monosaccharides arabinose 11.4% glucose 16.0%galactose 3.3% mannose 1.5% rhamnose 0.5% others 3.3% of dry solids(e.g. furfural)

[0132] The fermentation of the posthydrolysate, the recovery of ethanoland the crystallization of xylitol were carried out as described in thepreceding examples.

EXAMPLE 5 Production of Ethanol and Xylitol from Oat Hulls

[0133] Oat hull mass having the carbohydrate composition in Table 8 wasused as a starting materials. TABLE 8 xylan 26.5% of dry solids glucan30.7% araban  3.0% galactan  1.3% mannan  0.2%

[0134] The oat hull mass was hydrolyzed at a pressure of 2.4 MPa (350psi) at 235 degrees C., and the delay time was 2.0 minutes. Thehydrolyzed material contained 39.1% of dry solids, and the content ofdissolved solids was 36.4% of dry solids. The filtrate contained 12.0%of monosaccharides, 12.9% of acetic acid and 0.5% of furfural calculatedon dry solids. Posthydrolysis was performed on the filtrate by adjustingthe pH to 1 with sulphuric acid and by hydrolyzing the solution for 4hours at a pressure of 101 kPa (one atmosphere) at 100 degrees C. Thecomposition of the posthydrolysate is shown in Table 9: TABLE 9oligosaccharicles 1.3% of dry solids monosaccharides 63.1% xylose 69.0%of the monosaccharicles arabinose 6.9% glucose 19.1% galactose 3.1%mannose 0.8% rhamnose 1.1% Others (e.g. furfural) 2.8% of dry solids

[0135] The fermentation of the posthydrolysate, the recovery of ethanoland the crystallization of xylitol were carried out as described in thepreceding examples.

EXAMPLE 6 Steam Explosion and Extraction of Birch

[0136] A steam explosion treatment was carried out on birch chips with afactory-scale equipment at a temperature of 215 degrees C. with a delaytime of 4.5 minutes. The manufacturer of the equipment used is Technip,type of apparatus Stake II System.

[0137] The steam explosion product was suspended in hot process water ina mixing container to produce a fibrous suspension of about 3.5%.Therefrom the slurry was directed via an overflow to form a smooth layeron a 5-phase band filter operating on the countercurrent principle (typeA 40-1325; manufacturer Filters Philippe; width of wire 2.7 m; wiresupplied by manufacturer of apparatus). The solid mass was furtherextracted with hot water on the wire. The aqueous solution obtained isshown in Table 10. TABLE 10 dry solids content 8.7% by weight xylosemonomers 1.1% of natural weight xylose oligomers 3.7% of natural weightGlucose 0.04% of natural weight

EXAMPLE 7 Enzymatic Degradation of Steam-exploded Water-washed BirchChip Mass

[0138] The composition of the steam-exploded (215 degrees C./4.5 min.)birch chip mass (prepared in accordance with Example 6) used as rawmaterial for the hydrolysis is shown in Table 11. TABLE 11 dry solids32% cellulose 60% of dry solids xylan 3.6% of dry solids lignin(extractable in acetone) 25% of dry solids Klason lignin 12.3% of drysolids

[0139] 90 kg of the above-described mass was weighed into a reactionvessel provided with a stirrer and a heating jacket and containing 370 lof water. The mixture was heated to 50 degrees C., the pH was adjustedto 4.8-5.0, whereafter the enzyme solutions were added (1.24 l ofMultifect® L 250, 0.11 l of Novozyme™ (9188 and 0.09 l of Multifect® K).As activity units, the added quantities correspond to 6 FPU/g ofcellulase, 5 IU/g of beta-glucosidase and 0.02 ml of growth solution/gof mass dry solids of hemicellulase (18 U/g of dry solids of xylanase, 9nkat/p of dry solids of β-xylosidase, 2 nkat/g of dry solids ofesterase). The reaction was allowed to continue under the conditionsdescribed above for 18 hours. Thereafter mass and enzymes were added inthe same quantities as in the starting phase. A corresponding mass andenzyme addition was repeated after 21 hours from the start. Thereafterthe hydrolysis reaction was allowed to continue so that the total timewas 40 hours. The enzyme action was then stopped by heating the massmixture to 80 degrees C. for 10-20 minutes. In that connection, theremaining solid matter was solidified and thereby made easier toseparate. The solid matter and the solution were separated from oneanother by centrifugation (Pennvalt Sharples P600 model). The solutionwas further clarified by separating the remaining fine precipitate in aseparator (Westfalia model NA7-06-076). The solution was concentrated to33% DS for fermentation by evaporating with a Luwa evaporator in vacuoat a temperature of 40-50 degrees C.

[0140] Hydrolysis yields of steam exploded, water washed birch chip massin enzyme treatment are shown in Table 12. TABLE 12 % in solution yield% of dry solids conversion % glucose 3.3 24.5 40.8 xylose 0.4 2.6 72.0oligosaccharicles 0.7

[0141] Composition of the clarified and evaporated enzyme hydrolysatesolution are shown in Table 13. TABLE 13 glucose 22.7% of natural weightxylose 2.7% of natural weight oligosaccharicles 4.7% of natural weight

EXAMPLE 8 Fermentation of Enzymatic Hydrolysate of Steam Exploded, WaterWashed Birch Chip Mass into Ethanol

[0142] The hydrolyzed cellulose was fermented with a yeast Candidatropicalis ATCC 9968. A New Brunswick Scientific IF-250 fermentor wasused.

[0143] The fermentation solution is shown in Table 14. TABLE 14 451hydrolysate 1.5 kg Gistex yeast extract 401 water

[0144] The inoculation cultures were grown in two steps, first in a 2 lErlemneyer flask in an Orbital Shaker at 30 degrees C. for 2 days, thenin a New Brunswick Scientific SF-1 16 laboratory fermentor having anoperating volume of 11 l. The fermentor was aerated 5.5 N1/min. (0.5vvm) and stirred at a rate of 500 rpm. The culturing lasted for one day.

[0145] The actual fermentation was carried out on a pilot scale, theoperating volume being 100 l. The fermentor was aerated 25 NI/min (0.25vvm) and stirred at a rate of 100 rpm. The temperature was adjusted to30° C., and the foam was controlled with Plurior antifoaming agent.

[0146] The results of the fermentation are set forth in Table 15. TABLE15 time (h) cell mass (g/l) glucose (g/l) ethanol (g/l) 0  1.8 105.0 1.9 19.5 11.3 0 51.2 52 — 0 48.1 66 0 45.0

[0147] In the course of 29.5 hours, the yeast consumed all of theglucose in the substrate, producing ethanol therefrom with a yield of48%.

[0148] After fermentation, the yeast cells were separated from thesolution by centrifugation (Westfalia NA7-06-076). The clarifiedsolution was distilled to recover the ethanol.

EXAMPLE 9 Recovery of Ethanol from the Fermentation Product of EnzymaticHydrolysate of Steam Exploded, Water Washed Birch Chip Mass

[0149] 100 litres of fermented cellulose hydrolysate were distilled. Thefermentation had been carried out in the manner described in Example 8and clarified by centrifugation in a Westfalia NA7-06-076 separator. Theethanol content of the solution was 3.4%.

[0150] The distillation apparatus was constructed of standard componentsby Corning Process Systems which were of borosilicate glass. Thediameter of the column was 10 cm. The apparatus comprised 15 separationsteps: boiler, 13 bubble plates and a feed plate between the fourth andfifth bubble plates seen from the top. The distillation was carried outat a pressure of 100 mbar, at a feed rate of 10 l/h and with a refluxratio of 3:1. 8.5 kg of distillate were recovered, having an ethanolcontent of 36.0%. The ethanol content of the bottom product was 0.1%.

EXAMPLE 10 Chromatographic Separation of Xylose from Acid HydrolyzedBarley Hulls

[0151] The post hydrolysate solution prepared according to Example 4 wassubjected to a chromatographic separation in a chromatographicseparation column. Separation was made with a Na⁺-form separation resinin a pilot chromatographic separation column as a batch process.

[0152] The equipment comprised: a feed tank, a feed pump, a heatexchanger, the column, product containers, pipelines and valves forinput and output of solutions, eluent water devices, and instruments forthe flow control and for the determination of density, conductivity andtemperature of the outflow.

[0153] The pilot batch separation was made with a strong acid cationexchange resin (manufactured by Finex Oy, Finland) having thecross-linkage degree of 5,5% DVB and the average particle size of 0,35mm. 1.5 m³ of this resin was put into a pilot batch separation columnhaving a diameter of 0,6 m and regenerated into sodium (Na⁺) -form.

[0154] The temperature of the process was 65 degrees C. and the flowrate was adjusted to 0.7 m/h which was continuously controlled by valvefrom the bottom of the separation column.

[0155] The solution was concentrated to 30 g DS/100 g and the pH of thefeed solution was adjusted to pH 5,5 with 50 wt % NaOH solution andfiltered with a pressure filter using diatomaceous earth as filter aid.

[0156] The feed solution was pumped through the heat exchanger and thefeeding device to the top of the resin bed in the column. The feedsolution was moved downwards by feeding ion exchanged water to the topof the column. The density and the conductivity of the out comingsolution was measured generally continuously and according to thisinformation the outflow was collected and divided into three fractions:residual fraction (containing salts and small amounts of sugars),recycle fraction (containing e.g. glucose, galactose, xylose andarabinose) and xylose-fraction.

[0157] Furthermore, the xylose fraction was taken in two different ways:

[0158] The xylose fraction was taken as one fraction, which was thenfermented into ethanol and xylitol. Composition of fractions whiletaking xylose fraction as one fraction are shown in Table 16.

[0159] The amount of dry substance as well as the contents of xylose andother analyzed sugars of the feed solution and product fractions of theseparation are also shown in Table 16. The xylose yield was calculatedfrom the amount of the component in the particular fraction in relationto the total amount of that component in all out-coming fractions. TABLE16 Xylose fraction is taken as one fraction Composition and Yields FeedResidual Xylose solution fraction fraction Recycle fraction fraction dry36 16.9 16.4 2.7 solids, kg dry solids 30 7.3 12.3 7.4 content g/100 goligosaccharides, 1.3 % on dry solids Monosaccharides 45.2 % on drysolids Xylose % on dry 30.4 1.8 59.9 31.0 solids glucose, % on 7.2 4.59.8 10.1 dry solids arabinose, % on 5.2 0.4 9.4 9.1 dry solidsgalactose + 1.7 0.2 3.2 2.0 rhamnose, % on dry solids mannose, % on .070.1 1.2 0.8 dry solids xylose, yield % 97.1

[0160] The xylose fraction was also divided into two fractions;

[0161] 1. Xylose I-fraction which contained xylose and most of theglucose and

[0162] 2. Xylose II-fraction which contained most of the xylose andarabinose The xylose I-fraction was fermented into ethanol and xylitol.Xylose of the Xylose II-fraction was crystallized and crystallizationrun-off was used e.g. for recovery of additional xylose.

[0163] The composition of the fractions are shown in Table 17.

[0164] The amount of dry substance as well as the contents of xylose andother analyzed sugars of the feed solution and product fractions of theseparation are also shown in Table 17. The xylose yield was calculatedfrom the amount of the component in the particular fraction in relationto the total amount of that component in all out-coming fractions. TABLE17 Xylose fraction is taken as two fractions: xylose-I and xylose-IIComposition And Yields Xylose Feed Residual Xylose II- Recycle solutionfraction I-fraction fraction fraction fraction dry solids, 36 15.6 7.110.9 2.5 kg Dry solids content 30 7.8 8.5 13.1 7.6 g/100 goligosaccharides, % 1.3 on dry solids 1.3 Monosaccharides, 45.2 % on drysolids - xylose, % on dry 30.4 0.6 48.1 61.9 30.1 solids - glucose, % ondry 7.2 1.1 25.7 5.4 1.6 solids - arabinose, % on 5.2 0.5 0.0 13.4 12.9dry solids galactose + 1.7 0.1 3.6 3.0 1.4 rhamnose, % on dry solids -mannose, % on 0.7 0.0 1.1 1.3 0.8 dry solids xylose, yield % 33.3 65.9

EXAMPLE 11 Fermentation of Xylose Fraction with Candida shehatae

[0165] Fermentation of the xylose fraction, which was taken as onefraction ( example 10, Table 16) from the chromatographic separationstep was accomplished with Candida shehatae.

[0166] The xylose fraction from the separation step was sterilized for15 min at 120 degrees C. and mixed with a separately sterilized nutrientsolution. The composition of the final mixture was the following: xylose60 g/l, glucose 10 g/l, diammoniumphosphate 3 g/l, yeast extract 1g/l+traces of the other sugars present in the xylose fraction. Themixture was inoculated with an overnight aerobic culture of Candidashehatae CBS 2779 yeast strain produced on MYXP medium (maltose 3 g/l,yeast extract 3 g/l, xylose 20 g/l and peptone 5 g/l). The amount of theinoculum was 10 vol %. The fermentation was performed at oxygenlimitation (oxygen transfer rate appr. 4 mmol/lh) and at 30 degrees C.After 72 hours fermentation: 24 g/l ethanol and 7 g/l xylitol wasanalyzed.

EXAMPLE 12 Fermentation of Xylose Fraction with Pachysolen tannophilus

[0167] Fermentation of the xylose fraction (example 10, Table 16) whichwas taken as one fraction from the chromatographic separation step wasaccomplished with Pachysolen tannophilus. The fermentation was performedas in the previous example, but Pachysolen tannophilus NRRL Y-2460 yeaststrain was used instead of Candida shehatae. Oxygen transfer rate wasappr. 2,5 mmol/lh. After 96 hours fermentation 28 g/l xylitol and 18 g/lethanol was analyzed by HPLC.

EXAMPLE 13 Fermentation of Xylose I Fraction with Candida shehatae

[0168] Fermentation of the xylose I fraction (Example 10, Table 17) fromthe chromatographic separation was accomplished with Candida shehatae.The xylose fraction I and a nutrient solution were mixed as in theprevious examples, producing a composition of 30 g/l xylose, 16 g/lglucose, 3 g/l diammoniumphosphate, 1 g/l yeast extract and traces ofother components from the xylose I fraction. Fermentation was carriedout anaerobically, but otherwise as in example 10. The composition ofthe fermentation broth at 80 hours was 19 g/l ethanol and 6 g/l xylitol.

EXAMPLE 14 Nanofiltration of a Spent Sulphite Pulping Liquor as aPretreatment Step Using Various Membranes at Various pH Values

[0169] This example illustrates the effect of the membrane and pH on theperformance of nanofiltration (filtrations C1, C3, C6 and C8). Theliquor to be treated was a diluted runoff of the xylose crystallizationof a Mg-based sulphite spent pulping liquor obtained from beecbwoodpulping, which had been chromatographically purified using an ionexchange resin in Mg²⁺ form. The pH of the solution was adjusted to thedesired value (see Table 18) with MgO. Before the nanofiltration, theliquor was pretreated by dilution (filtrations C1 and C3), by filtrationthrough a filter paper (filtration C6) or with MgO dosing combined withfiltration through a filter paper (filtrations C7 and C8).

[0170] A batch mode nanofiltration was carried out using a laboratorynanofiltration equipment consisting of rectangular cross-flow flat sheetmodules with a membrane area of 0.0046 m². Both the permeate and theretentate were recycled back to the feed vessel (total recycling modefiltration). The feed volume was 20 liters. During the filtration, thecross-flow velocity was 6 m/s and the pressure was 18 bar. Thetemperature was kept at 40 degrees C.

[0171] Table 18 presents the results of the total recycling modefiltrations. The flux values in Table 18 were measured after 3 hours offiltration. Table 18 shows the dry substance content (DS) in the feed(%), the xylose content in the feed and in the permeate (based on thedry substance content), the permeate flux at a pressure of 18 bar andthe flux reduction caused by fouling. The membranes were Desal-5 DK andNTR-7450.

[0172] RDS refers to the refractomeric dry substance content expressedas % by weight. TABLE 18 Nanofiltration of Spent Sulphite Pulping LiquorXylose in Xylose in Foul- Filtration No., DS in the feed, permeate, Fluxing, membrane pH feed, w-% % on DS % on RDS l/(m²h) % C1, 3.4 8.1 22.627.4 31 1 Desal-5 -DK C6* 3.4 9.7 20.3 33.5 23 1 Desal-5-DK C7* 5.9 8.221.7 55.2 58 3 Desal-5-DK C3, 3.4 7.6 24.3 29.9 25 29 NTR-7450 C8, 6.18.3 21.8 34.5 43 25 NTR-7450 C8, 6.1 8.3 21.8 45 30 1 Desal-5-DK

[0173] The results of Table 18 show that nanofiltration provides xyloseconcentrations of 1.5 to 2.5 times those of the feed. When the pH in thefeed is high, the xylose content on RDS in the permeate is high forexample when pH is 5.9 or 6.1. Furthermore, the flux was improved evento two-fold at higher pH values.

EXAMPLE 15 Pretreatment with Ultrafiltration

[0174] Concentration mode ultrafiltrations DU1 and DU2 were carried outusing an RE filter (rotation-enhanced filter). In this filter, the bladerotates near the membrane surface minimizing the concentrationpolarization during the filtration. The filter was a home-madecross-rotational filter. The rotor speed was 700 rpm. In filtration DU1,the membrane was C5F UF (a membrane of regenerated cellulose having acut-off size of 5000 g/mol, manufacturer Hoechst/Celgard). In filtrationDU2, the membrane was Desal G10 (a thin film membrane having a cut-offsize of 2500 g/mol, manufacturer Osmonics/Desal).

[0175] Concentration mode filtrations were made using a Mg-basedsulphite spent pulping liquor obtained from beechwood pulping. Thefiltration was carried out at a temperature of 35° C. and a pH of 3.6.The results are presented in Table 19. TABLE 19 Pretreatment withUltrafiltration of Mg-Based Sulphite Spent Pulping Liquor Xylose inXylose in Filtration DS in feed, Filtration feed, permeate, No. Membrane% time % on DS % on RDS DU1 C5F 14.4  1 hour 16.3 23.2 DU1 C5F 22.0 23hours 9.2 20.0 DU2 Desal G10 12.2  3 days 12.7 41.6

EXAMPLE 16 Nanofiltration

[0176] A one-day laboratory-scale experiment where the permeate wascollected out was carried out with the same equipment as in Example 14and are shown in Table 20 below (filtrations DN1 and DN2). The liquor tobe treated was a Mg-based sulphite spent pulping liquor obtained frombeechwood pulping.

[0177] In filtration DN1 of Table 20, the ultrafiltered spent liquor(DU1 using a C5F membrane) was used as the feed solution. The pH of thesolution was adjusted to 4.5 using MgO, and the liquor was prefilteredthrough a filter paper before nanofiltration. Nanofiltration was carriedout at a pressure of 19 bar and at a temperature of 40 degrees C.

[0178] Filtration DN2 of Table 20 was carried out using the dilutedoriginal spent liquor. Its pH had been adjusted to 4.8 and the solutionwas prefiltered through a filter paper before nanofiltration. Thenanofiltration was carried out at a pressure of 17 bar and at atemperature of 40 degrees C. After about 20 hours of filtration, apermeate volume of 5 liters and a concentrate volume of 20 liters wereobtained.

[0179] Both filtrations DN1 and DN2 of Table 20 were carried out at across-flow velocity of 6 m/s. Fouling was about 1% in both filtrations.The nanofiltration membrane in both filtrations DN1 and DN2 in Table 20was Desal-5 DK.

[0180] In each filtration DN1 and DN2 of Table 20, the nanofiltrationmembrane was pretreated in three different ways: (1) no pretreatment,(2) washing the membrane with ethanol, and (3) washing the membrane withan alkaline detergent. The results are set forth in Table 20: TABLE 20Nanofiltration of Mg-Based Sulphite Spent Pulping Liquor Xylose inXylose permeate, % Flux, DS in feed, in feed, on RDS l/m²h) FiltrationpH % % on DS (1)/(2)/(3) at 20 h DN1 4.5 10.7 21.1 24/35/49 14 (19 bar)DN2 4.6 12.3 16.8 N.A.*/35/34 22/32 (17/19 bar)

[0181] Although embodiments and examples of this invention have beenshown and described, it is to be understood that various modifications,substitutions, and rearrangements of equipment and method (process)steps, as well as the use of various feed solutions, different microbes,and recovery of various products, can be made by those skilled in theart without departing from the novel spirit and scope of this invention.

What is claimed is:
 1. A method of processing lignocellulose-containingmaterial from xylan-containing biomass comprising pentoses and hexosesto produce ethanol and xylitol, comprising the steps of: processinglignocellulose-containing material from xylan-containing biomasscomprising pentoses and hexoses to produce a processed solutioncomprising free pentoses and hexoses, said processing comprisinghydrolysis and/or partial hydrolysis of said lignocellulose-containingmaterial; said lignocellulose-containing material comprising at leastone lignocellulosic material selected from the group consisting ofcellulose and hemicellulose; said pentose comprising at least onepentose-containing material selected form the group consisting of xyloseand arabinose; said hexose comprising at least one hexose-containingmaterial selected from the group consisting of glucose, galactose,rhamnose and/or mannose,; said xylan-containing matter selected from thegroup consisting of wood, hardwood as alder, aspen, birch, beech,eucalyptus, poplar, willow and maple, softwood as pine and spruce,plants, plant constituents, grains as wheat, barley, rice, rye and oat,particulates of grain as straw, hulls, husks, fiber, stems, shells, corncobs, corn straw , corn fiber, nutshells, almond shells, coconut shells,bagasse, cotton seed bran, cotton seed skins, wood chips, sawdust,woodpulp, processed paper, spent sulphite liquor, spent liquor frompaper processing, spent liquor from woodpulp processing, sulphitecooking liquor, and liquids derived from any of the preceding;fermenting said processed solution with microbes to produce a fermentedsolution comprising fermented ethanol, xylitol and spent microbes, saidfermenting comprising converting said hexose in said processed solutionto ethanol and converting said pentoses to xylitol or xylitol andethanol; said microbes comprising at least one fermenting microorganismselected form the group consisting of naturally occurring bacteria,recombinant bacteria, naturally occurring yeast, recombinant yeast, andfungi; and distilling fermented liquid derived from said fermentedsolution to produce distilled ethanol, said distilled ethanol comprisinga greater concentration of ethanol by weight on a liquid basis than saidethanol in said fermented solution.
 2. A method according to claim 1wherein: said fermented solution comprises fermented xylitol; saidfermenting comprises reducing xylose in said processed solution tofermented xylitol; said distilling further produces xylitol bottomproduct comprising distilled xylitol; and said xylitol bottom productcomprises a greater concentration of distilled xylitol by weight on drysubstance (solids) basis than said fermented xylitol in said fermentedsolution.
 3. A method according to claim 2 further comprising:separating said xylitol bottom product to produce a xylitol product andresidue; and said xylitol product comprises a greater concentration ofxylitol by weight on a dry substance (solids) basis than said distilledxylitol in said xylitol bottom product.
 4. A method according to claim 3wherein: said separating comprises chromatographic separation; and saidchromatographic separation is selected from the group consisting ofbatch separation, continuous simulated moving bed separation, andsequential simulated moving bed separation.
 5. A method according toclaim 3 wherein: said separating comprising filtering; and saidfiltering is selected from the group consisting of membrane filtration,ultrafiltration, nanofiltration, and microfiltration.
 6. A methodaccording to claim 5 wherein: said filtering comprises passing saidxylitol bottom product through at least one membrane; and said membraneis selected from the group consisting of a high shear membrane, avibrating membrane, a rotating membrane, a flat sheet membrane, atubular membrane, a spiral membrane, a hollow fiber membrane, a neutralcharged membrane, an ionic membrane, a cationic membrane, and an anionicmembrane.
 7. A method according to claim 3 further comprisingcrystallizing said xylitol product to produce xylitol crystals.
 8. Amethod according to claim 7 wherein said crystallization is coolingcrystallization.
 9. A method according to claim 7 wherein said xylitolcrystals are separated by centrifugation and filtration and washed withwater to produce substantially pure crystalline xylitol.
 10. A methodaccording to claim 1 including removing solids from said processedsolution.
 11. A method according to claim 1 including: separating asubstantial portion of said spent microbes from said fermented solutionprior to distilling to produce said fermented liquid derived from saidfermented solution; said fermented liquid comprising ethanol, and saidfermented liquid comprising substantially less spent microbes by weighton a dry substance (solids) basis that said spent microbes in saidfermented solution; and said separating of said substantial portion ofsaid spent microbes from said fermented solution comprising at least oneseparating method selected from the group consisting of filtration,centrifugation and decanting.
 12. A method according to claim 1 whereinprocessing of said lignocellulose-containing material comprises at leastone of the following: prehydrolysis of said lignocellulose-containingmaterial, steam explosion of said lignocellulose-containing material,enzymatic hydrolysis of said lignocellulose-containing material withenzymes having a cellulolytic and hemicellulolytic activity to hydrolyzesaid lignocellulose-containing material, acid hydrolysis of saidlignocellulose-containing material, chromatographic separation, membranefiltration, ion-exchange purification, precipitation, partial hydrolysisof said lignocellulose-containing material, and extraction of saidlignocellulose-containing material.
 13. A method according to claim 1wherein said processed solution comprises biomass hydrolysates.
 14. Amethod according to claim 13 wherein said biomass hydrolysates areobtained by a process selected from the group consisting of direct acidhydrolysis of said biomass, enzymatic prehydrolysate obtained byprehydrolysis of said biomass with steam or acetic acid, acid hydrolysisof prehydrolysate obtained by prehydrolysis of said biomass with steamor acetic acid, autohydrolysis using water or steam, and a sulphitepulping process.
 15. A method according to claim 13 wherein said biomasshydrolysates are selected from the group consisting of: spent sulphitepulping liquor, acid spent sulphite liquor, spent liquor from hardwoodpulping, spent liquor from softwood pulping before hexoses are removed,spent liquor from softwood pulping after hexoses are removed, spentliquor from digestion of said biomass, spent liquor from hydrolysis ofsaid biomass, spent liquor from solvent-based pulping, spent liquor fromphenol based pulping, spent liquor from formic acid based pulping, spentliquor from ethanol-based pulping, mother liquor from crystallization ofxylose, and diluted runoff of xylose crystallization of sulphite spentpulping liquor based fraction/solution.
 16. A method according to claim1 wherein: said pentose in said processed solution comprises arabinose;and said arabinose is reduced to arabinitol during said fermentation.17. A method according to claim 1 wherein: said processing comprisespartially hydrolyzing said lignocellulose-containing material;separating said partially hydrolyzed lignocellulose-containing materialinto an extracted biomass comprising hexosans, and a prehydrolyzatecomprising free xylose; hydrolyzing said extracted biomass to produce anhydrolyzate comprising hexoses; said fermenting comprises fermentingsaid hydrolyzate to produce a fermented solution comprising ethanol; andfermenting said prehydrolyzate to produce a fermented solutioncomprising xylitol or xylitol and ethanol.
 18. A method according toclaim 1 including post processing said processed solution in at leastone post processing step selected from the group consisting of:crystallization, purification, chromatography, membrane filtration,ion-exchange, concentration, evaporation, reverse osmosis, colorremoval, reduction, detoxification, and catalytic hydrogenation.
 19. Amethod according to claim 1 wherein said processed solution isdetoxified to help remove inhibitors prior to fermenting by one or moreof the following: liming, calcium hydroxide addition, sodium hydroxideaddition, pH adjustment, concentration, filtering, activated charcoaltreatment, extraction with organic solvents, ion exchange, ionexclusion, molecular sieve treatment, steam stripping, heating, removingfurfural, stripping volatile compounds, and reducing of said processedsolution by sulphite addition.
 20. A method according to claim 1wherein: said naturally occurring bacteria is selected from the groupconsisting of Bacillus macerans DMS 1574, Bacteroides polypragmatus NRCC2288, Clostridium saccharolyticum ATCC 35040, C. thermohydrosulfurcium39E, C. thermohydrosulfuricum ATCC 31925, Erwinia chrysanthemi 8374,Thermoanaerobacter ethanolicus ATTC 31938, Lactobacillus brevis, andLacococcus lactis ssp. Lactis; said recombinant bacteria is selectedfrom the group consisting of Erwinia chrysanthemi 8374, Escherichia coliB, E. coli B K011, Klebsiella oxytoca M5A1, K. planticola SDF20,Zymomonas mobilis CP4, and Z. mobilis NRRL 14023; said naturallyoccurring yeast is selected from the group consisting of Candida blankiATCC 18736, C. acidothermophilum ATCC 20831, C. brassicae ATCC 32196, C.famata, C. fructus JCM 1513, C. guilliermondii ATCC22017, C. shehataeCBS 4705, C. shehatae CSIR Y492, C. shehatae ATCC
 22984. sp CSIR 62 A/2,C. tenuis CBS 4435, C. tropicalis KY 5014, C. tropicalis ATCC 20240, C.tropicalis ATCC 9968, C. tropicalis NRRL y 11860, Clavispora sp. UWO83-833-1, Kluyveromyces cellobiovous KV 5199, K. marxianus, Pachysolentannophilus NRRL Y 2460, P. tannophilus RL 171, Pichia segobiensis CBS6857, P. stipitis CBS 5773, P. stipitis CBS 5776, P. stipitis NRRL Y1714, Schizosaccharomyces pombe ATCC 2478, Hansenula anomala ATCC 34080,Kluyveromyces fragilis ATCC 12424, Saccharomyces uvarum ATCC 24556, S.uvarum ATCC 26602, F. oxysporum, and Debaryomyces hansenii; saidrecombinant yeast is selected from the group consisting ofSaaccharomyces cerevisiae, S. cerevisiae TJ1, S. cerevisiae H550, S.cerevisiae ATCC 24860, Schizosaccharomyces pombe ATCC 2456, and S. pombeNRRL Y164; and said fungi is selected from the group consisting ofAureobasidium pullulans, Fusarium avenaceium VTT-D-80146, F.clamydosporum VTT-D-77055, F. culmorum VTT-D-80148, F. graminearumVTT-D-79129, F. lycopersici ATCC 15417, F. oxysporum VTT-D-80134, F.sembucium VTT-D-77056, F. solani VTT-D-80139, Monilia sp., Mucor sp.105, Neurospora crassa NCIM 870, and Paecilmyces sp. NFI ATCC
 20766. 21.A method according to claim 1 wherein said fermenting microorganism is ayeast selected from the group consisting of a yeast of the generaCandida, Pichia, Pachysolen, or Debaryomyces.
 22. A method according toclaim 21 wherein said yeast is selected form the group consisting ofgenera Candida tropicalis, Candida tropicalis ATCC 9968, Pachysolentannophilus, and Debaryomyces hansenii.
 23. A method according to claim22 wherein said fermenting occurs at a temperature ranging from about 10to about 45 degrees C. at a pH ranging from 4 to 7 with a yeastconcentration of about 1 to about 40 g of dry yeast per liter ofprocessed solution for about 24 to about 96 hours in the presence of atleast one nutrient.
 24. A method according to claim 23 wherein saidnutrient is selected from the group consisting of yeast extract,diammoniumphosphate, peptone, biotin, thiamin, folic acid, a watersoluble vitamin, a fat soluble vitamin, vitamin A, vitamin B complex,vitamin D, vitamin E, vitamin K, vitamin B1, vitamin B2, vitamin B5,vitamin B6, vitamin B12, vitamin B15, and a vitamin.
 25. A methodaccording to claim 1 including crystallizing said xylitol to producecrystalline xylitol.
 26. A method according to claim 1 wherein saidxylitol comprises liquid xylitol.
 27. A method of processinglignocellulose-containing material from xylan-containing biomasscomprising pentoses and hexoses to produce ethanol and xylitol,comprising the steps of: hydrolyzing lignocellulose-containing materialfrom xylan-containing biomass comprising pentoses and hexoses to producea hydrolyzed solution comprising free pentoses and hexoses; saidlignocellulose-containing material comprising at least onelignocellulosic material selected from the group consisting ofcellulose, hemicellulose, said pentose comprising at least onepentose-containing material selected form the group consisting of xyloseand arabinose; said hexose comprising at least one hexose-containingmaterial selected from the group consisting of glucose, galactose,rhamnose, mannose, and other monosaccharides; said xylan-containingmatter selected from the group consisting of wood, hardwood as alder,aspen, birch, beech, maple, eucalyptus, willow, and poplar, softwood aspine and spruce, plants, plant constituents, grain as wheat, barley,rice, rye and oat particulates of grains as straw, hulls, husks, stems,fiber, shells , corn cobs, corn stems, corn fibres, nutshells, almondshells, coconut shells, bagasse, cotton seed bran, cotton seed skins,wood chips, sawdust, woodpulp, processed paper, spent sulphite liquor,spent liquor from hardwood pulping, spent liquor from paper processing,spent liquor from woodpulp processing, sulphite cooking liquor, andliquids derived from any of the preceding; fermenting said hydrolyzedsolution with microbes to produce a fermented solution comprisingfermented ethanol, fermented xylitol, fermented xylose, and spentmicrobes, said fermenting comprising converting a substantial amount ofsaid hexose in said hydrolyzed solution to fermented ethanol andreducing a substantial amount of said pentose in said hydrolyzedsolution to fermented xylitol, fermented ethanol solution and fermentedxylose; said microbes comprising at least one fermenting microorganismselected form the group consisting of naturally occurring bacteria,recombinant bacteria, naturally occurring yeast, recombinant yeast, andfungi; and distilling fermented liquid derived from said fermentedsolution to produce distilled ethanol and a distilled solutioncomprising distilled xylitol solution, distilled xylose and spentmicrobes, said distilled ethanol comprising a greater concentration ofdistilled ethanol by weight on a liquid basis than said fermentedethanol in said fermented solution, said distilled solution having agreater concentration of distilled xylitol solution by weight on a drysubstance (solids) basis than said fermented xylitol solution in saidfermented solution; and separating said distilled solution byfractionating said distilled solution into fractions comprising aseparated xylitol-producing fraction and a separated xylose fraction,said separated xylitol-producing fraction comprising a greaterconcentration of xylitol-producing solution by weight on a dry substance(solids) basis than said distilled xylitol-producing solution in saiddistilled solution.
 28. A method according to claim 27 includingcrystallizing said xylitol to produce crystalline xylitol.
 29. A methodaccording to claim 27 wherein said xylitol comprises liquid xylitol. 30.A method according to claim 27 wherein: said hydrolyzed solution issubjected to at least one treatment selected from the group consistingof: pH adjustment, concentration, filtration, filtering with a pressurefilter, filtering with diatomaceous earth, chromatographic separation,detoxification, removing inhibitors, overliming, calcium hydroxideaddition, sodium hydroxide addition, activated charcoal, extraction withorganic solvents, ion exchange, ion exclusion, molecular sieves, steamstripping, heating, removing furfural, stripping volatile compounds, andreduction of said hydrolyzed solution by sulphite addition; said xylitolsolution selected from the group consisting of a xylitol-rich solutionand a xylose-rich solution; said xylitol solution having a greaterconcentration of at least one compound on a dry substance (solids) basisthan said compound in said hydrolyzed solution; and said compound isselected from the group consisting of xylitol, xylose, arabinose,mannose, and galactose and rhamnose.
 31. A method according to claim 30wherein: said separating comprises chromatographic separation; and saidchromatographic separation is selected from the group consisting ofbatch separation, continuous simulated moving bed separation, andsequential simulated moving bed separation.
 32. A method according toclaim 30 wherein: said separating comprising filtering; and saidfiltering is selected from the group consisting of membrane filtration,ultrafiltration, nanofiltration, and microfiltration.
 33. A methodaccording to claim 32 wherein: said filtering comprises passing saiddistilled solution through at least one membrane; and said membrane isselected from the group consisting of a high shear membrane, a vibratingmembrane, a rotating membrane, a flat sheet membrane, a tubularmembrane, a spiral membrane, a hollow fiber membrane, a neutral chargedmembrane, an ionic membrane, a cationic membrane, and an anionicmembrane.
 34. A method according to claim 27 further comprisingcrystallizing said xylitol fraction to produce xylitol crystals.
 35. Amethod according to claim 34 wherein said crystallization is selectedfrom the group consisting of cooling crystallization.
 36. A methodaccording to claim 35 wherein said xylitol crystals are separated bycentrifugation or filtration and washed with water to producesubstantially pure crystalline xylitol.
 37. A method according to claim27 including hydrogenating said separated xylose fraction to producehydrogenated xylitol.
 38. A method according to claim 37 furthercomprising crystallizing said hydrogenated xylitol to produce xylitolcrystals.
 39. A method according to claim 27 including: separating asubstantial portion of said spent microbes from said fermented solutionprior to said distilling to produce said fermented liquid derived fromsaid fermented solution; said fermented liquid comprising fermentedethanol, fermented xylitol, fermented xylose, and spent microbes; saidfermented liquid comprising substantially less spent microbes by weighton a dry substance (solids) basis that said spent microbes in saidfermented solution; and said separating of said substantial portion ofsaid spent microbes from said fermented solution comprising at least oneseparating method selected from the group consisting of filtration,centrifigation, and decanting.
 40. A method according to claim 27including removing a substantial amount of solids from said hydrolyzedsolution before fermenting, said removing comprising at least oneremoval step selected from the group consisting of filtration,centrifugation and decanting.
 41. A method according to claim 27 whereinsaid hydrolyzing is selected from the group consisting of: enzymatichydrolysis of said lignocellulose-containing material with enzymeshaving a cellulolytic and xylanolytic activity to hydrolyze saidlignocellulose-containing material, and acid hydrolysis of saidlignocellulose-containing material.
 42. A method according to claim 27including pretreatment of said lignocellulose-containing material beforesaid hydrolyzing, said pretreatment comprising at least one pretreatmentmethod selected from the group consisting of prehydrolysis of saidlignocellulose-containing material, steam explosion of saidlignocellulose-containing material, alkaline treatment, solventextraction, partial hydrolysis of said lignocellulose-containingmaterial, and extraction by alkali, NaOH, NH4OH of saidlignocellulose-containing material.
 43. A method according to claim 27wherein said hydrolyzed solution comprises biomass hydrolysates.
 44. Amethod according to claim 43 wherein said biomass hydrolysates areobtained by a process selected from the group consisting of direct acidhydrolysis of said biomass, enzymatic prehydrolysate obtained byprehydrolysis of said biomass with steam or acetic acid; acid hydrolysisof prehydrolysate obtained by prehydrolysis of said biomass with steamor acetic acid, a sa-prehydrolysis process, autohydrolysis using wateror steam, and a sulphite pulping process.
 45. A method according toclaim 43 wherein said biomass hydrolysates are selected from the groupconsisting of: spent sulphite pulping liquor, acid spent sulphiteliquor, spent liquor from hardwood pulping, spent liquor from softwoodpulping before hexoses are removed, spent liquor from softwood pulpingafter hexoses are removed, spent liquor from digestion of said biomass,spent liquor from hydrolysis of said biomass, spent liquor fromsolvent-based pulping, spent liquor from phenol based pulping, spentliquor from formic acid based pulping, spent liquor from ethanol-basedpulping, mother liquor from crystallization of xylose, and dilutedrunoff of xylose crystallization of sulphite spent pulping liquor basedliquor
 46. A method according to claim 27 wherein: said pentose in saidprocessed solution comprises arabinose; and said arabinose is reduced toarabinitol during said fermentation.
 47. A method according to claim 27wherein: said naturally occurring bacteria is selected from the groupconsisting of Bacillus macerans DMS 1574, Bacteroides polypragmatus NRCC2288, Clostridium saccharolyticum ATCC 35040, C. thermohydrosulfruricum39E, C. thermohydrosulfuricum ATCC 31925, Erwinia chrysanthemi 8374,Thermoanaerobacter ethanolicus ATTC 31938, Lactobacillus brevis, andLacococcus lactis ssp. Lactis; said recombinant bacteria is selectedfrom the group consisting of Erwinia chrysanthemi 8374, Escherichia coliB, E. coli B K011, Klebsiella oxytoca M5A1, K. planticola SDF20,Zymomonas mobilis CP4, and Z. mobilis NRRL 14023; said naturallyoccurring yeast is selected from the group consisting of Candida blankiATCC 18736, C. acidothermophilum ATCC 20831, C. brassicae ATCC 32196, C.famata, C. fructus JCM 1513, C. guilliermondii ATCC22017, C. shehataeCBS 4705, C. shehatae CSIR Y492, C. shehatae ATCC
 22984. sp CSIR 62 A/2,C. tenuis CBS 4435, C. tropicalis KY 5014, C. tropicalis ATCC 20240, C.tropicalis ATCC 9968, C. tropicalis NRRL y 11860, Clavispora sp. UWO83-833-1, Kluyveromyces cellobiovous KV 5199, K. marxianus, Pachysolentannophilus NRRL Y 2460, P. tannophilus RL 171, Pichia segobiensis CBS6857, P. stipitis CBS 5773, P. stipitis CBS 5776, P. stipitis NRRL Y1714, Schizosaccharomyces pombe ATCC 2478, Hansenula anomala ATCC 34080,Kluyveromyces fragilis ATCC 12424, Saccharomyces uvarum ATCC 24556, S.uvarum ATCC 26602, F. oxysporum, and Debaryomyces hansenii; saidrecombinant yeast is selected from the group consisting ofSaaccharomyces cerevisiae, S. cerevisiae TJ1, S. cerevisiae H550, S.cerevisiae ATCC 24860, Schizosaccharomyces pombe ATCC 2456, and S. pombeNRRL Y164; and said fungi is selected from the group consisting ofAureobasidium pullulans, Fusarium avenaceium VTT-D-80146, F.clamydosporum VTT-D-77055, F. culmorum VTT-D-80148, F. graminearumVTT-D-79129, F. lycopersici ATCC 15417, F. oxysporum VTT-D-80134, F.sembucium VTT-D-77056, F solani VTT-D-80139, Monilia sp., Mucor sp. 105,Neurospora crassa NCIM 870, and Paecilmyces sp. NFI ATCC
 20766. 48. Amethod according to claim 27 wherein said fermenting microorganism is ayeast selected from the group consisting of a yeast of the generaCandida, Pichia, Pachysolen, or Debaryomyces.
 49. A method according toclaim 48 wherein said yeast is selected form the group consisting ofgenera Candida tropicalis, Candida tropicalis ATCC 9968, Pachysolentannophilus, and Debaryomyces hansenii.
 50. A method according to claim49 wherein said fermenting occurs at a temperature ranging from about 10to about 45 degrees C. at a pH ranging from 4 to 7 with a yeastconcentration of about 1 to about 40 g of dry yeast per liter ofhydrolyzed solution for about 24 to about 96 hours in the presence of atleast one nutrient.
 51. A method according to claim 49 wherein saidnutrient is selected from the group consisting of yeast extract,diammoniumphosphate, peptone, biotin, thiamin, folic acid, a watersoluble vitamin, a fat soluble vitamin, vitamin A, vitamin B complex,vitamin D, vitamin E, vitamin K, vitamin B1, vitamin B2, vitamin B5,vitamin B6, vitamin B12, vitamin B15, and a vitamin.
 52. A method ofprocessing lignocellulose-containing material from xylan-containingbiomass comprising pentoses and hexoses to produce ethanol and xylitol,comprising the steps of: partially hydrolyzing lignocellulose-containingmaterial from xylan-containing matter in biomass comprising pentoses andhexoses to produce a partially hydrolyzed solution comprising freepentoses and hexoses, pentosans, and hexosans; saidlignocellulose-containing material comprising at least onelignocellulosic material selected from the group consisting ofcellulose, hemicellulose; said pentoses comprising at least onepentose-containing material selected form the group consisting of xyloseand arabinose; said hexoses comprising at least one hexose-containingmaterial selected from the group consisting of glucose, galactose,rhamnose and mannose; said xylan-containing matter selected from thegroup consisting of wood, hardwood as alder, aspen, birch, beech,eucalyptus, poplar, willow and maple, softwood as pine and spruce,willow, plants, plant constituents, grains as wheat, barley, rye, riceand oat particulates of grain as straw, hulls, husks, fiber, stems,shells, corn cobs, cornstraw, corn fiber, nutshells, almond shells,coconut shells, bagasse, cotton seed bran, cotton seed skins, woodchips, sawdust, woodpulp, processed paper, spent sulphite liquor, spentliquor from hardwood pulping, spent liquor from paper processing, spentliquor from woodpulp processing, sulphite cooking liquor, and liquidsderived from any of the preceding; separating said partially hydrolyzedsolution into an extracted biomass and solubles, said extracted masscomprising pentosans and hexosans, and solids, said solubles comprisingxylose, soluble xylans, pentoses, soluble pentosans and residue;hydrolyzing said extracted biomass to produce a hydrolyzed biomasscomprising hydrolyzed hexoses, hydrolyzed pentoses, and hydrolyzedsolids, said hydrolyzing converting a substantial amount of saidpentosans to pentoses, and said hydrolyzing converting a substantialamount of said hexosans to hexoses; separating said hydrolyzed biomassinto a separated biomass solution and solids, said separated biomasssolution comprising pentoses and hexoses, said separated biomasssolution comprising a greater concentration of pentoses by weight on adry substance (solids) basis than said hydrolyzed pentoses in saidhydrolyzed biomass, said separated biomass solution comprising a greaterconcentration of hexoses by weight on a dry substance (solids) basisthan said hydrolyzed hexoses in said hydrolyzed biomass; fractionatingsaid solubles to separate said solubles into fractions comprising axylose-rich fraction, and a residue (residual) fraction, saidxylose-rich fraction comprising a higher concentration of xylose byweight on a dry substance (solids) than said xyloses in said solubles,said residue fraction comprising a higher concentration of residue byweight on a dry substance (solids) than said residue in said solubles,said xylose-rich fraction comprising a higher concentration of at leastone compound by weight on a dry substance (solids) than said compound insaid other fractions, and said compound being selected from the groupconsisting of xylose, xylitol, arabinose, mannose, and galactose andrhanmose; hydrogenating said xylose-rich fraction to producehydrogenated xylitol, said hydrogenated xylitol having a greaterconcentration of xylitol by weight on a dry substance (solids) basisthan said xylitols in said solubles; fermenting said xylose-containingfraction and said separated biomass solution with microbes to produce afermented solution comprising fermented ethanol and spent microbes, saidfermenting comprising converting a substantial amount of said xyloses insaid xylose-containing fraction to fermented ethanol and part to xylitoland reducing a substantial amount of said pentoses and hexoses in saidseparated biomass solution to fermented ethanol; and said microbescomprising at least one fermenting microorganism selected form the groupconsisting of naturally occurring bacteria, recombinant bacteria,naturally occurring yeast, recombinant yeast, and fungi.
 53. A methodaccording to claim 52 including crystallizing said xylitol to producecrystalline xylitol.
 54. A method according to claim 52 wherein saidxylitol comprises liquid xylitol.
 55. A method according to claim 52including distilling fermented liquid derived from said fermentedsolution to produce a distilled solution comprising distilled ethanol,said distilled ethanol comprising a greater concentration of ethanol byweight on a liquid basis than said fermented ethanol in said fermentedsolution.
 56. A method according to claim 55 including: separating asubstantial portion of said spent microbes from said fermented solutionprior to said distilling and optionally before to said distilling toproduce said fermented liquid derived from said fermented solution; saidfermented liquid comprising fermented ethanol and spent microbes; saidfermented liquid comprising substantially less spent microbes by weighton a dry substance (solids) basis that said spent microbes in saidfermented solution; and said separating of said substantial portion ofsaid spent microbes from said fermented solution comprising at least oneseparating method selected from the group consisting of filtration,centrifugation, decanting, flocculation and flotation
 57. A methodaccording to claim 52 wherein separating of said hydrolyzed biomassincludes at least one separation method selected from the groupconsisting of: filtration of said hydrolyzed biomass, membranefiltration of said hydrolyzed biomass, ultrafiltration of saidhydrolyzed biomass, nanofiltration of said hydrolyzed biomass,microfiltration of said hydrolyzed biomass, centrifugation of saidhydrolyzed biomass, decanting of said hydrolyzed biomass, clarificationof said hydrolyzed biomass, crystallization of said hydrolyzed biomass,chromatography, ion exclusion, ion-exchange of said hydrolyzed biomass,concentration of said hydrolyzed biomass, evaporation of said hydrolyzedbiomass, reverse osmosis of said hydrolyzed biomass, color removal ofsaid hydrolyzed biomass, reduction of said hydrolyzed biomass,detoxification of said hydrolyzed biomass, and catalytic hydrogenationof said hydrolyzed biomass.
 58. A method according to claim 52 whereinsaid separated biomass solution is detoxified to help remove inhibitorsprior to fermenting with one or more of the following: liming, calciumhydroxide or calcium oxide addition, hydroxide addition e.g. NaOH, pHadjustment, activated charcoal treatment, extraction with organicsolvents, ion exchange, ion exclusion, molecular sieve treatment, steamstripping, heating, removing furfural, stripping volatile compounds, andreduction of said separated biomass solution by sulphite addition.
 59. Amethod according to claim 52 wherein said xylose-containing fraction isdetoxified to help remove inhibitors prior to fermenting by one or moreof the following: liming, calcium hydroxide or calcium oxide addition,hydroxide addition e.g. NaOH, pH adjustment, concentration, filtering,activated charcoal treatment, extraction with organic solvents, ionexchange, ion exclusion, molecular sieve treatment, steam stripping,heating, removing furfural, stripping volatile compounds, and reductionof said xylose-containing fraction by sulphite addition.
 60. A methodaccording to claim 52 including combusting at least some of said solidsin said extracted biomass prior to hydrolyzing said extracted biomass.61. A method according to claim 52 wherein: said fractionating compriseschromatographic separation; and said chromatographic separation isselected from the group consisting of batch separation, continuoussimulated moving bed separation, and sequential simulated moving bedseparation.
 62. A method according to claim 52 wherein: saidfractionating comprising filtering; and said filtering is selected fromthe group consisting of membrane filtration, ultrafiltration,nanofiltration, and microfiltration.
 63. A method according to claim 62wherein: said filtering comprises passing a solution comprising saidsolubles through at least one membrane; and said membrane is selectedfrom the group consisting of a high shear membrane, a vibratingmembrane, a rotating membrane, a flat sheet membrane, a tubularmembrane, a spiral membrane, a hollow fiber membrane, a neutral chargedmembrane, an ionic membrane, a cationic membrane, and an anionicmembrane.
 64. A method according to claim 52 wherein said hydrogenatingcomprises chemical hydrogenation.
 65. A method according to claim 52wherein said hydrogenating comprises biochemical hydrogenation.
 66. Amethod according to claim 52 further comprising crystallizing saidhydrogenated fraction to produce xylitol crystals.
 67. A methodaccording to claim 66 wherein said crystallization is coolingcrystallization
 68. A method according to claim 66 wherein said xylitolcrystals are separated by centrifugation or filtration and washed withwater to produce substantially pure crystalline xylitol.
 69. A methodaccording to claim 52 wherein said hydrolyzing is selected from thegroup consisting of: enzymatic hydrolysis of said extracted biomass withenzymes having a cellulolytic and xylanolytic activity to hydrolyze saidextracted biomass, and acid hydrolysis of said extracted biomass.
 70. Amethod according to claim 52 wherein said partially hydrolyzing of saidlignocellulose-containing material is selected from the group consistingof: steam explosion of said lignocellulose-containing material, partialenzymatic hydrolysis of said lignocellulose-containing material withenzymes having a cellulolytic and xylanolytic activity to partiallyhydrolyze said lignocellulose-containing material, partial acidhydrolysis of said lignocellulose-containing material, and subjectingsaid lignocellulose-containing material to acetic acid.
 71. A methodaccording to claim 52 wherein said partially hydrolyzed solution isseparated by at least one separation method selected form the groupconsisting of: centrifugation of said partially hydrolyzed solution,decanting of said partially hydrolyzed solution, clarification of saidpartially hydrolyzed solution, crystallization of said partiallyhydrolyzed solution, chromatography of said partially hydrolyzedsolution, ion-exchange, concentration of said partially hydrolyzedsolution, evaporation of said partially hydrolyzed solution, reverseosmosis of said partially hydrolyzed solution, catalytic hydrogenationof said partially hydrolyzed solution, filtration of said partiallyhydrolyzed solution, membrane filtration of said partially hydrolyzedsolution, ultrafiltration of said partially hydrolyzed solution,nanofiltration of said partially hydrolyzed solution, andmicrofiltration of said partially hydrolyzed solution.
 72. A methodaccording to claim 52 wherein said partially hydrolyzed solutioncomprises biomass hydrolysates.
 73. A method according to claim 72wherein said biomass hydrolysates are selected from the group consistingof: spent sulphite pulping liquor, acid spent sulphite liquor, spentliquor from softwood pulping before hexoses are removed, spent liquorfrom softwood pulping after hexoses are removed, spent liquor fromhardwood pulping, spent liquor from digestion of said biomass, spentliquor from hydrolysis of said biomass, spent liquor fromsa-prehydrolysis pulping, spent liquor from solvent-based pulping, spentliquor from phenol based pulping, spent liquor from formic acid basedpulping, spent liquor from ethanol-based pulping, mother liquor fromcrystallization of xylose, and diluted runoff of xylitol crystallizationof sulphite spent pulping liquor based fraction
 74. A method accordingto claim 52 wherein: said pentoses in said separated biomass solutioncomprises arabinose; and said arabinose is reduced to arabinitol duringsaid fermentation.
 75. A method according to claim 52 wherein: saidnaturally occurring bacteria is selected from the group consisting ofBacillus macerans DMS 1574, Bacteroides polypragmatus NRCC 2288,Clostridium saccharolyticum ATCC 35040, C. thermohydrosulfuricum 39E, C.thermohydrosulfuricum ATCC 31925, Erwinia chrysanthemi 8374,Thermoanaerobacter ethanolicus ATTC 31938, Lactobacillus brevis, andLacococcus lactis ssp. Lactis; said recombinant bacteria is selectedfrom the group consisting of Erwinia chrysanthemi 8374, Escherichia coliB, E. coli B K011, Klebsiella oxytoca M5A1, K. planticola SDF20,Zymomonas mobilis CP4, and Z. mobilis NRRL 14023; said naturallyoccurring yeast is selected from the group consisting of Candida blankiATCC 18736, C. acidothermophilum ATCC 20831, C. brassicae ATCC 32196, C.famata, C. fructus JCM 1513, C. guilliermondii ATCC22017, C. shehataeCBS 4705, C. shehalae CSIR Y492, C. shehatae ATCC
 22984. sp CSIR 62 A/2,C. tenuis CBS 4435, C. tropicalis KY 5014, C. tropicalis ATCC 20240, C.tropicalis ATCC 9968, C. tropicalis NRRL y 11860, Clavispora sp. UWO83-833-1, Kluyveromyces cellobiovous KV 5199, K. marxianus, Pachysolentannophilus NRRL Y 2460, P. tannophilus RL 171, Pichia segobiensis CBS6857, P. stipitis CBS 5773, P. stipitis CBS 5776, P. stipitis NRRL Y1714, Schizosaccharomyces pombe ATCC 2478, Hansenula anomala ATCC 34080,Kluyveromyces fragilis ATCC 12424, Saccharomyces uvarum ATCC 24556, S.uvarum ATCC 26602, F. oxysporum, and Debaryomyces hansenii; saidrecombinant yeast is selected from the group consisting ofSaaccharomyces cerevisiae, S. cerevisiae TJ1, S. cerevisiae H550, S.cerevisiae ATCC 24860, Schizosaccharomyces pombe ATCC 2456, and S. pombeNRRL Y164; and said fungi is selected from the group consisting ofAureobasidium pullulans, Fusarium avenaceium VTT-D-80146, F.clamydosporum VTT-D-77055, F. culmorum VTT-D-80148, F. graminearumVTT-D-79129, F. lycopersici ATCC 15417, F. oxysporum VTT-D-80134, F.sembucium VTT-D-77056, F. solani VTT-D-80139, Monilia sp., Mucor sp.105, Neurospora crassa NCIM 870, and Paecilmyces sp. NFI ATCC
 20766. 76.A method according to claim 52 wherein said fermenting microorganism isa yeast selected from the group consisting of a yeast of the generaCandida, Pichia, Pachysolen, or Debaryomyces.
 77. A method according toclaim 76 wherein said yeast is selected form the group consisting ofgenera Candida tropicalis, Candida tropicalis ATCC 9968, Pachysolentannophilus, and Debaryomyces hansenii.
 78. A method according to claim77 wherein said fermenting occurs at a temperature ranging from about 10to about 45 degrees C. at a pH ranging from 4 to 7 with a yeastconcentration of about 1 to about 40 g of dry yeast per liter ofsolution comprising said xylose-containing fraction and said separatedbiomass solution, for about 24 to about 96 hours in the presence of atleast one nutrient.
 79. A method according to claim 78 wherein saidnutrient is selected from the group consisting of yeast extract,diammoniumphosphate, peptone, biotin, thiamin, folic acid, a watersoluble vitamin, a fat soluble vitamin, vitamin A, vitamin B complex,vitamin D, vitamin E, vitamin K, vitamin B1, vitamin B2, vitamin B5,vitamin B6, vitamin B12, vitamin B15, and a vitamin.